diff --git a/build.gradle b/build.gradle
new file mode 100644
index 0000000..3f39f6b
--- /dev/null
+++ b/build.gradle
@@ -0,0 +1,39 @@
+
+plugins {
+    id 'java-library'
+}
+
+repositories {
+    mavenLocal()
+    mavenCentral()
+}
+
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(17)
+    }
+}
+
+compileJava {
+    options.compilerArgs << '-Xlint:unchecked'
+    options.compilerArgs << '-Xlint:rawtypes'
+    options.release = 17
+}
+
+compileTestJava {
+    options.compilerArgs << '-Xlint:unchecked'
+    options.compilerArgs << '-Xlint:rawtypes'
+    options.release = 17
+}
+
+dependencies {
+    api 'io.vavr:vavr:0.10.4'
+
+    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
+    testImplementation("org.mockito:mockito-core:4.5.1")
+    testImplementation("org.mockito:mockito-junit-jupiter:4.5.1")
+}
+
+tasks.named('test') {
+    useJUnitPlatform()
+}
\ No newline at end of file
diff --git a/lib/build.gradle b/lib/build.gradle
deleted file mode 100644
index 3f39f6b..0000000
--- a/lib/build.gradle
+++ /dev/null
@@ -1,39 +0,0 @@
-
-plugins {
-    id 'java-library'
-}
-
-repositories {
-    mavenLocal()
-    mavenCentral()
-}
-
-java {
-    toolchain {
-        languageVersion = JavaLanguageVersion.of(17)
-    }
-}
-
-compileJava {
-    options.compilerArgs << '-Xlint:unchecked'
-    options.compilerArgs << '-Xlint:rawtypes'
-    options.release = 17
-}
-
-compileTestJava {
-    options.compilerArgs << '-Xlint:unchecked'
-    options.compilerArgs << '-Xlint:rawtypes'
-    options.release = 17
-}
-
-dependencies {
-    api 'io.vavr:vavr:0.10.4'
-
-    testImplementation 'org.junit.jupiter:junit-jupiter:5.8.1'
-    testImplementation("org.mockito:mockito-core:4.5.1")
-    testImplementation("org.mockito:mockito-junit-jupiter:4.5.1")
-}
-
-tasks.named('test') {
-    useJUnitPlatform()
-}
\ No newline at end of file
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java b/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
deleted file mode 100644
index d934c88..0000000
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
+++ /dev/null
@@ -1,18 +0,0 @@
-/*
- * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
- * Distributed under the terms of the MIT License
- */
-package com.github.tonivade.vavr.effect;
-
-public sealed interface Fiber<T> {
-
-  IO<T> join();
-  
-  IO<Unit> cancel();
-  
-  static <T> Fiber<T> of(IO<T> join, IO<Unit> cancel) {
-    return new FiberImpl<>(join, cancel);
-  }
-  
-  record FiberImpl<T>(IO<T> join, IO<Unit> cancel) implements Fiber<T> {}
-}
\ No newline at end of file
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java b/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java
deleted file mode 100644
index aa179af..0000000
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/IO.java
+++ /dev/null
@@ -1,880 +0,0 @@
-/*
- * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
- * Distributed under the terms of the MIT License
- */
-package com.github.tonivade.vavr.effect;
-
-import static io.vavr.Function1.identity;
-import java.time.Duration;
-import java.util.ArrayDeque;
-import java.util.Deque;
-import java.util.NoSuchElementException;
-import java.util.Objects;
-import java.util.concurrent.CancellationException;
-import java.util.concurrent.CompletableFuture;
-import java.util.concurrent.Executor;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
-import java.util.concurrent.atomic.AtomicReference;
-import java.util.function.Consumer;
-import java.util.function.Predicate;
-import java.util.function.Supplier;
-import java.util.function.UnaryOperator;
-import io.vavr.CheckedConsumer;
-import io.vavr.CheckedRunnable;
-import io.vavr.Function1;
-import io.vavr.Function2;
-import io.vavr.PartialFunction;
-import io.vavr.Tuple;
-import io.vavr.Tuple2;
-import io.vavr.collection.HashMap;
-import io.vavr.collection.List;
-import io.vavr.collection.Seq;
-import io.vavr.concurrent.Future;
-import io.vavr.concurrent.Promise;
-import io.vavr.control.Either;
-import io.vavr.control.Option;
-import io.vavr.control.Try;
-
-public sealed interface IO<T> {
-
-  IO<Unit> UNIT = pure(Unit.unit());
-
-  default Future<T> runAsync() {
-    return runAsync(this, IOConnection.UNCANCELLABLE).future();
-  }
-
-  default Future<T> runAsync(Executor executor) {
-    return forked(executor).andThen(this).runAsync();
-  }
-  
-  default T unsafeRunSync() {
-    return safeRunSync().get();
-  }
-
-  default Try<T> safeRunSync() {
-    return runAsync().toTry();
-  }
-
-  default void safeRunAsync(Consumer<? super Try<? extends T>> callback) {
-    safeRunAsync(Future.DEFAULT_EXECUTOR, callback);
-  }
-
-  default void safeRunAsync(Executor executor, Consumer<? super Try<? extends T>> callback) {
-    runAsync(executor).onComplete(callback);
-  }
-
-  default <R> IO<R> map(Function1<? super T, ? extends R> map) {
-    return flatMap(map.andThen(IO::pure));
-  }
-
-  default <R> IO<R> flatMap(Function1<? super T, ? extends IO<? extends R>> map) {
-    return new FlatMapped<>(this, map.andThen(IO::narrowK));
-  }
-
-  default <R> IO<R> andThen(IO<? extends R> after) {
-    return flatMap(ignore -> after);
-  }
-
-  default <R> IO<R> ap(IO<Function1<? super T, ? extends R>> apply) {
-    return parMap2(Future.DEFAULT_EXECUTOR, this, apply, (v, a) -> a.apply(v));
-  }
-
-  default IO<Try<T>> attempt() {
-    return map(Try::success).recover(Try::failure);
-  }
-
-  default IO<Either<Throwable, T>> either() {
-    return attempt().map(Try::toEither);
-  }
-
-  default <L, R> IO<Either<L, R>> either(Function1<? super Throwable, ? extends L> mapError,
-                                         Function1<? super T, ? extends R> mapper) {
-    return either().map(either -> either.bimap(mapError, mapper));
-  }
-
-  default <R> IO<R> redeem(Function1<? super Throwable, ? extends R> mapError,
-                           Function1<? super T, ? extends R> mapper) {
-    return attempt().map(result -> result.fold(mapError, mapper));
-  }
-
-  default <R> IO<R> redeemWith(Function1<? super Throwable, IO<? extends R>> mapError,
-                               Function1<? super T, IO<? extends R>> mapper) {
-    return attempt().flatMap(result -> result.fold(mapError, mapper));
-  }
-
-  default IO<T> recover(Function1<? super Throwable, ? extends T> mapError) {
-    return recoverWith(partialFunction(x -> true, mapError.andThen(IO::pure)));
-  }
-
-  @SuppressWarnings("unchecked")
-  default <X extends Throwable> IO<T> recover(Class<X> type, Function1<? super X, ? extends T> function) {
-    return recoverWith(partialFunction(error -> error.getClass().equals(type), t -> function.andThen(IO::pure).apply((X) t)));
-  }
-  
-  @SuppressWarnings("serial")
-  static <A, B> PartialFunction<A, B> partialFunction(Predicate<? super A> matcher, Function1<? super A, ? extends B> function) {
-    return new PartialFunction<>() {
-      
-      @Override
-      public boolean isDefinedAt(A value) {
-        return matcher.test(value);
-      }
-      
-      @Override
-      public B apply(A t) {
-        return function.apply(t);
-      }
-    };
-  }
-
-  default IO<T> recoverWith(PartialFunction<? super Throwable, IO<? extends T>> mapper) {
-    return new Recover<>(this, mapper);
-  }
-
-  default IO<Tuple2<Duration, T>> timed() {
-    return IO.task(System::nanoTime).flatMap(
-      start -> map(result -> Tuple.of(Duration.ofNanos(System.nanoTime() - start), result)));
-  }
-  
-  default IO<Fiber<T>> fork() {
-    return async(callback -> {
-      IOConnection connection = IOConnection.cancellable();
-      Promise<T> promise = runAsync(this, connection);
-      
-      IO<T> join = fromFuture(promise.future());
-      IO<Unit> cancel = exec(connection::cancel);
-      
-      callback.accept(Try.success(Fiber.of(join, cancel)));
-    });
-  }
-
-  default IO<T> timeout(Duration duration) {
-    return timeout(Future.DEFAULT_EXECUTOR, duration);
-  }
-  
-  default IO<T> timeout(Executor executor, Duration duration) {
-    return racePair(executor, this, sleep(duration)).flatMap(either -> either.fold(
-        ta -> ta._2().cancel().map(x -> ta._1()),
-        tb -> tb._1().cancel().flatMap(x -> IO.raiseError(new TimeoutException()))));
-  }
-
-  default IO<T> repeat() {
-    return repeat(1);
-  }
-
-  default IO<T> repeat(int times) {
-    return repeat(this, unit(), times);
-  }
-
-  default IO<T> repeat(Duration delay) {
-    return repeat(delay, 1);
-  }
-
-  default IO<T> repeat(Duration delay, int times) {
-    return repeat(this, sleep(delay), times);
-  }
-
-  default IO<T> retry() {
-    return retry(1);
-  }
-
-  default IO<T> retry(int maxRetries) {
-    return retry(this, unit(), maxRetries);
-  }
-
-  default IO<T> retry(Duration delay) {
-    return retry(delay, 1);
-  }
-
-  default IO<T> retry(Duration delay, int maxRetries) {
-    return retry(this, sleep(delay), maxRetries);
-  }
-
-  @SuppressWarnings("unchecked")
-  static <T> IO<T> narrowK(IO<? extends T> value) {
-    return (IO<T>) value;
-  }
-
-  static <T> IO<T> pure(T value) {
-    return new Pure<>(value);
-  }
-  
-  static <A, B> IO<Either<A, B>> race(IO<? extends A> fa, IO<? extends B> fb) {
-    return race(Future.DEFAULT_EXECUTOR, fa, fb);
-  }
-  
-  static <A, B> IO<Either<A, B>> race(Executor executor, IO<? extends A> fa, IO<? extends B> fb) {
-    return racePair(executor, fa, fb).flatMap(either -> either.fold(
-        ta -> ta._2().cancel().map(x -> Either.left(ta._1())),
-        tb -> tb._1().cancel().map(x -> Either.right(tb._2()))));
-  }
-  
-  static <A, B> IO<Either<Tuple2<A, Fiber<B>>, Tuple2<Fiber<A>, B>>> racePair(Executor executor, IO<? extends A> fa, IO<? extends B> fb) {
-    return cancellable(callback -> {
-      
-      IOConnection connection1 = IOConnection.cancellable();
-      IOConnection connection2 = IOConnection.cancellable();
-      
-      Promise<A> promiseA = runAsync(IO.forked(executor).andThen(fa), connection1);
-      Promise<B> promiseB = runAsync(IO.forked(executor).andThen(fb), connection2);
-
-      promiseA.future().onComplete(result -> callback.accept(
-          result.map(a -> Either.left(Tuple.of(a, Fiber.of(IO.fromFuture(promiseB.future()), IO.exec(connection2::cancel)))))));
-      promiseB.future().onComplete(result -> callback.accept(
-          result.map(b -> Either.right(Tuple.of(Fiber.of(IO.fromFuture(promiseA.future()), IO.exec(connection2::cancel)), b)))));
-
-      return IO.exec(() -> {
-        try {
-          connection1.cancel();
-        } finally {
-          connection2.cancel();
-        }
-      });
-    });
-  }
-
-  static <T> IO<T> raiseError(Throwable error) {
-    return new Failure<>(error);
-  }
-
-  static <T> IO<T> delay(Duration delay, Supplier<? extends T> lazy) {
-    return sleep(delay).andThen(task(lazy));
-  }
-
-  static <T> IO<T> suspend(Supplier<IO<? extends T>> lazy) {
-    return new Suspend<>(lazy);
-  }
-
-  static <T, R> Function1<T, IO<R>> lift(Function1<T, R> task) {
-    return task.andThen(IO::pure);
-  }
-
-  public static <A, B> Function1<A, IO<B>> liftOption(Function1<? super A, ? extends Option<? extends B>> function) {
-    return value -> fromOption(function.apply(value));
-  }
-
-  public static <A, B> Function1<A, IO<B>> liftTry(Function1<? super A, ? extends Try<? extends B>> function) {
-    return value -> fromTry(function.apply(value));
-  }
-
-  public static <A, B> Function1<A, IO<B>> liftEither(Function1<? super A, ? extends Either<Throwable, ? extends B>> function) {
-    return value -> fromEither(function.apply(value));
-  }
-
-  static <T> IO<T> fromOption(Option<? extends T> task) {
-    return fromEither(toEither(task));
-  }
-
-  static <T> IO<T> fromTry(Try<? extends T> task) {
-    return fromEither(task.toEither());
-  }
-
-  static <T> IO<T> fromEither(Either<Throwable, ? extends T> task) {
-    return task.fold(IO::raiseError, IO::pure);
-  }
-  
-  static <T> IO<T> fromFuture(Future<? extends T> promise) {
-    CheckedConsumer<Consumer<? super Try<? extends T>>> callback = promise::onComplete;
-    return async(callback);
-  }
-  
-  static <T> IO<T> fromCompletableFuture(CompletableFuture<? extends T> promise) {
-    return fromFuture(Future.fromCompletableFuture(promise));
-  }
-
-  static IO<Unit> sleep(Duration duration) {
-    return sleep(Future.DEFAULT_EXECUTOR, duration);
-  }
-
-  static IO<Unit> sleep(Executor executor, Duration duration) {
-    return cancellable(callback -> {
-      Future<Unit> sleep = FutureModule.sleep(executor,duration)
-        .onComplete(result -> callback.accept(Try.success(Unit.unit())));
-      return IO.exec(() -> sleep.cancel(true));
-    });
-  }
-
-  static IO<Unit> exec(CheckedRunnable task) {
-    return task(asSupplier(task));
-  }
-
-  static <T> IO<T> task(Supplier<? extends T> producer) {
-    return new Delay<>(producer);
-  }
-
-  static <T> IO<T> never() {
-    return async(callback -> {});
-  }
-  
-  static IO<Unit> forked() {
-    return forked(Future.DEFAULT_EXECUTOR);
-  }
-  
-  static IO<Unit> forked(Executor executor) {
-    return async(callback -> executor.execute(() -> callback.accept(Try.success(Unit.unit()))));
-  }
-
-  static <T> IO<T> async(CheckedConsumer<Consumer<? super Try<? extends T>>> callback) {
-    return cancellable(asFunction(callback));
-  }
-
-  static <T> IO<T> cancellable(Function1<Consumer<? super Try<? extends T>>, IO<Unit>> callback) {
-    return new Async<>(callback);
-  }
-
-  static <A, T> IO<Function1<A, IO<T>>> memoize(Function1<A, IO<T>> function) {
-    return memoize(Future.DEFAULT_EXECUTOR, function);
-  }
-
-  static <A, T> IO<Function1<A, IO<T>>> memoize(Executor executor, Function1<A, IO<T>> function) {
-    var ref = Ref.make(HashMap.<A, Promise<T>>empty());
-    return ref.map(r -> {
-      Function1<A, IO<IO<T>>> result = a -> r.modify(map -> map.get(a).fold(() -> {
-        Promise<T> promise = Promise.make();
-        function.apply(a).safeRunAsync(executor, promise::tryComplete);
-        return Tuple.of(IO.fromFuture(promise.future()), map.put(a, promise));
-      }, promise -> Tuple.of(IO.fromFuture(promise.future()), map)));
-      return result.andThen(io -> io.flatMap(identity()));
-    });
-  }
-
-  static IO<Unit> unit() {
-    return UNIT;
-  }
-
-  static <T, R> IO<R> bracket(IO<? extends T> acquire, 
-      Function1<? super T, ? extends IO<? extends R>> use, Function1<? super T, IO<Unit>> release) {
-    return cancellable(callback -> {
-      
-      IOConnection cancellable = IOConnection.cancellable();
-      
-      Promise<? extends T> promise = runAsync(acquire, cancellable);
-      
-      promise.future()
-        .onFailure(error -> callback.accept(Try.failure(error)))
-        .onSuccess(resource -> runAsync(use.andThen(IO::narrowK).apply(resource), cancellable).future()
-          .onComplete(result -> runAsync(release.andThen(IO::narrowK).apply(resource), cancellable).future()
-            .onComplete(ignore -> callback.accept(result))
-        ));
-      
-      return IO.exec(cancellable::cancel);
-    });
-  }
-
-  static <T, R> IO<R> bracket(IO<? extends T> acquire, 
-      Function1<? super T, ? extends IO<? extends R>> use, CheckedConsumer<? super T> release) {
-    return bracket(acquire, use, asFunction(release));
-  }
-
-  static <T extends AutoCloseable, R> IO<R> bracket(IO<? extends T> acquire, 
-      Function1<? super T, ? extends IO<? extends R>> use) {
-    return bracket(acquire, use, AutoCloseable::close);
-  }
-
-  static IO<Unit> sequence(Seq<IO<?>> sequence) {
-    IO<?> initial = IO.unit();
-    return sequence.foldLeft(initial, (IO<?> a, IO<?> b) -> a.andThen(b)).andThen(IO.unit());
-  }
-
-  static <A> IO<Seq<A>> traverse(Seq<IO<A>> sequence) {
-    return traverse(Future.DEFAULT_EXECUTOR, sequence);
-  }
-
-  static <A> IO<Seq<A>> traverse(Executor executor, Seq<IO<A>> sequence) {
-    return sequence.foldLeft(pure(List.empty()), 
-        (IO<Seq<A>> xs, IO<A> a) -> parMap2(executor, xs, a, Seq::append));
-  }
-
-  static <A, B, C> IO<C> parMap2(IO<? extends A> fa, IO<? extends B> fb,
-                              Function2<? super A, ? super B, ? extends C> mapper) {
-    return parMap2(Future.DEFAULT_EXECUTOR, fa, fb, mapper);
-  }
-
-  static <A, B, C> IO<C> parMap2(Executor executor, IO<? extends A> fa, IO<? extends B> fb,
-                              Function2<? super A, ? super B, ? extends C> mapper) {
-    return cancellable(callback -> {
-      
-      IOConnection connection1 = IOConnection.cancellable();
-      IOConnection connection2 = IOConnection.cancellable();
-      
-      Promise<A> promiseA = runAsync(IO.forked(executor).andThen(fa), connection1);
-      Promise<B> promiseB = runAsync(IO.forked(executor).andThen(fb), connection2);
-      
-      promiseA.future().onComplete(a -> promiseB.future().onComplete(b -> callback.accept(map2(a, b, mapper))));
-      
-      return IO.exec(() -> {
-        try {
-          connection1.cancel();
-        } finally {
-          connection2.cancel();
-        }
-      });
-    });
-  }
-
-  static <A, B> IO<Tuple2<A, B>> tuple(IO<? extends A> fa, IO<? extends B> fb) {
-    return tuple(Future.DEFAULT_EXECUTOR, fa, fb);
-  }
-
-  static <A, B> IO<Tuple2<A, B>> tuple(Executor executor, IO<? extends A> fa, IO<? extends B> fb) {
-    return parMap2(executor, fa, fb, Tuple::of);
-  }
-
-  private static <T> Promise<T> runAsync(IO<T> current, IOConnection connection) {
-    return runAsync(current, connection, new CallStack<>(), Promise.make());
-  }
-
-  private static <A, B, C> Try<? extends C> map2(Try<A> a, Try<B> b, Function2<? super A, ? super B, ? extends C> mapper) {
-    return a.flatMap(x -> b.map(y -> mapper.apply(x, y)));
-  }
-
-  private static <T> Either<Throwable, T> toEither(Option<? extends T> task) {
-    return task.fold(() -> Either.left(new NoSuchElementException()), Either::right);
-  }
-
-  private static Supplier<Unit> asSupplier(CheckedRunnable task) {
-    return () -> {
-      task.unchecked().run();
-      return Unit.unit();
-    };
-  }
-
-  private static <T> Function1<T, IO<Unit>> asFunction(CheckedConsumer<? super T> release) {
-    return t -> {
-      release.unchecked().accept(t);
-      return unit();
-    };
-  }
-
-  @SuppressWarnings("unchecked")
-  private static <T, U, V> Promise<T> runAsync(IO<T> current, IOConnection connection, CallStack<T> stack, Promise<T> promise) {
-    while (true) {
-      try {
-        current = unwrap(current, stack, identity());
-        
-        if (current instanceof Pure<T> pure) {
-          return promise.success(pure.value);
-        }
-        
-        if (current instanceof Async<T> async) {
-          return executeAsync(async, connection, promise);
-        }
-        
-        if (current instanceof FlatMapped) {
-          stack.push();
-
-          var flatMapped = (FlatMapped<U, T>) current;
-          IO<U> source = IO.narrowK(unwrap(flatMapped.current, stack, u -> u.flatMap(flatMapped.next)));
-          
-          if (source instanceof Async<U> async) {
-            Promise<U> nextPromise = Promise.make();
-            
-            nextPromise.future().andThen(tryU -> tryU.onFailure(promise::failure)
-                .onSuccess(u -> runAsync(IO.narrowK(flatMapped.next.apply(u)), connection, stack, promise)));
-            
-            executeAsync(async, connection, nextPromise);
-            
-            return promise;
-          }
-
-          if (source instanceof Pure<U> pure) {
-            Function1<? super U, IO<T>> andThen = flatMapped.next.andThen(IO::narrowK);
-            current = andThen.apply(pure.value);
-          } else if (source instanceof FlatMapped) {
-            FlatMapped<V, U> flatMapped2 = (FlatMapped<V, U>) source;
-            current = flatMapped2.current.flatMap(a -> flatMapped2.next.apply(a).flatMap(flatMapped.next));
-          }
-        } else {
-          stack.pop();
-        }
-      } catch (Throwable error) {
-        Option<IO<T>> result = stack.tryHandle(error);
-        
-        if (result.isDefined()) {
-          current = result.get();
-        } else {
-          return promise.failure(error);
-        }
-      }
-    }
-  }
-
-  private static <T, U> IO<T> unwrap(IO<T> current, CallStack<U> stack, Function1<IO<? extends T>, IO<? extends U>> next) {
-    while (true) {
-      if (current instanceof Failure<T> failure) {
-        return stack.sneakyThrow(failure.error);
-      } else if (current instanceof Recover<T> recover) {
-        stack.add(partialFunction(recover.mapper::isDefinedAt, recover.mapper.andThen(next)));
-        current = recover.current;
-      } else if (current instanceof Suspend<T> suspend) {
-        Supplier<IO<T>> andThen = () -> IO.narrowK(suspend.lazy.get());
-        current = andThen.get();
-      } else if (current instanceof Delay<T> delay) {
-        return IO.pure(delay.task.get());
-      } else if (current instanceof Pure) {
-        return current;
-      } else if (current instanceof FlatMapped) {
-        return current;
-      } else if (current instanceof Async) {
-        return current;
-      } else {
-        throw new IllegalStateException();
-      }
-    }
-  }
-
-  private static <T> Promise<T> executeAsync(Async<T> current, IOConnection connection, Promise<T> promise) {
-    if (connection.isCancellable() && !connection.updateState(StateIO::startingNow).isRunnable()) {
-      return promise.complete(Try.failure(new CancellationException()));
-    }
-    
-    connection.setCancelToken(current.callback.apply(promise::tryComplete));
-    
-    promise.future().andThen(x -> connection.setCancelToken(UNIT));
-    
-    if (connection.isCancellable() && connection.updateState(StateIO::notStartingNow).isCancellingNow()) {
-      connection.cancelNow();
-    }
-
-    return promise;
-  }
-
-  private static <T> IO<T> repeat(IO<T> self, IO<Unit> pause, int times) {
-    return self.redeemWith(IO::raiseError, value -> {
-      if (times > 0) {
-        return pause.andThen(repeat(self, pause, times - 1));
-      } else return IO.pure(value);
-    });
-  }
-
-  private static <T> IO<T> retry(IO<T> self, IO<Unit> pause, int maxRetries) {
-    return self.redeemWith(error -> {
-      if (maxRetries > 0) {
-        return pause.andThen(retry(self, pause.repeat(), maxRetries - 1));
-      } else return IO.raiseError(error);
-    }, IO::pure);
-  }
-
-  final class Pure<T> implements IO<T> {
-
-    private final T value;
-
-    private Pure(T value) {
-      this.value = Objects.requireNonNull(value);
-    }
-
-    @Override
-    public String toString() {
-      return "Pure(" + value + ")";
-    }
-  }
-
-  final class Failure<T> implements IO<T> {
-
-    private final Throwable error;
-
-    private Failure(Throwable error) {
-      this.error = Objects.requireNonNull(error);
-    }
-
-    @Override
-    public String toString() {
-      return "Failure(" + error + ")";
-    }
-  }
-
-  final class FlatMapped<T, R> implements IO<R> {
-
-    private final IO<? extends T> current;
-    private final Function1<? super T, ? extends IO<? extends R>> next;
-
-    private FlatMapped(IO<? extends T> current,
-                         Function1<? super T, ? extends IO<? extends R>> next) {
-      this.current = Objects.requireNonNull(current);
-      this.next = Objects.requireNonNull(next);
-    }
-
-    @Override
-    public String toString() {
-      return "FlatMapped(" + current + ", ?)";
-    }
-  }
-
-  final class Delay<T> implements IO<T> {
-
-    private final Supplier<? extends T> task;
-
-    private Delay(Supplier<? extends T> task) {
-      this.task = Objects.requireNonNull(task);
-    }
-
-    @Override
-    public String toString() {
-      return "Delay(?)";
-    }
-  }
-
-  final class Async<T> implements IO<T> {
-
-    private final Function1<Consumer<? super Try<? extends T>>, IO<Unit>> callback;
-
-    private Async(Function1<Consumer<? super Try<? extends T>>, IO<Unit>> callback) {
-      this.callback = Objects.requireNonNull(callback);
-    }
-
-    @Override
-    public String toString() {
-      return "Async(?)";
-    }
-  }
-
-  final class Suspend<T> implements IO<T> {
-
-    private final Supplier<? extends IO<? extends T>> lazy;
-
-    private Suspend(Supplier<? extends IO<? extends T>> lazy) {
-      this.lazy = Objects.requireNonNull(lazy);
-    }
-
-    @Override
-    public String toString() {
-      return "Suspend(?)";
-    }
-  }
-
-  final class Recover<T> implements IO<T> {
-
-    private final IO<T> current;
-    private final PartialFunction<? super Throwable, ? extends IO<? extends T>> mapper;
-
-    private Recover(IO<T> current, PartialFunction<? super Throwable, ? extends IO<? extends T>> mapper) {
-      this.current = Objects.requireNonNull(current);
-      this.mapper = Objects.requireNonNull(mapper);
-    }
-
-    @Override
-    public String toString() {
-      return "Recover(" + current + ", ?)";
-    }
-  }
-}
-
-interface IOConnection {
-  
-  IOConnection UNCANCELLABLE = new IOConnection() {
-    @Override
-    public boolean isCancellable() { return false; }
-
-    @Override
-    public void setCancelToken(IO<Unit> cancel) { }
-
-    @Override
-    public void cancelNow() { }
-
-    @Override
-    public void cancel() { }
-
-    @Override
-    public StateIO updateState(UnaryOperator<StateIO> update) { return StateIO.INITIAL; }
-  };
-  
-  boolean isCancellable();
-
-  void setCancelToken(IO<Unit> cancel);
-  
-  void cancelNow();
-  
-  void cancel();
-  
-  StateIO updateState(UnaryOperator<StateIO> update);
-  
-  static IOConnection cancellable() {
-    return new IOConnection() {
-      
-      private IO<Unit> cancelToken;
-      private final AtomicReference<StateIO> state = new AtomicReference<>(StateIO.INITIAL);
-      
-      @Override
-      public boolean isCancellable() { return true; }
-      
-      @Override
-      public void setCancelToken(IO<Unit> cancel) { this.cancelToken = Objects.requireNonNull(cancel); }
-      
-      @Override
-      public void cancelNow() { cancelToken.runAsync(); }
-      
-      @Override
-      public void cancel() {
-        if (state.getAndUpdate(StateIO::cancellingNow).isCancelable()) {
-          cancelNow();
-        
-          state.set(StateIO.CANCELLED);
-        }
-      }
-      
-      @Override
-      public StateIO updateState(UnaryOperator<StateIO> update) {
-        return state.updateAndGet(update::apply);
-      }
-    };
-  }
-}
-
-final class StateIO {
-  
-  public static final StateIO INITIAL = new StateIO(false, false, false);
-  public static final StateIO CANCELLED = new StateIO(true, false, false);
-  
-  private final boolean isCancelled;
-  private final boolean cancellingNow;
-  private final boolean startingNow;
-  
-  public StateIO(boolean isCancelled, boolean cancellingNow, boolean startingNow) {
-    this.isCancelled = isCancelled;
-    this.cancellingNow = cancellingNow;
-    this.startingNow = startingNow;
-  }
-  
-  public boolean isCancelled() {
-    return isCancelled;
-  }
-  
-  public boolean isCancellingNow() {
-    return cancellingNow;
-  }
-  
-  public boolean isStartingNow() {
-    return startingNow;
-  }
-  
-  public StateIO cancellingNow() {
-    return new StateIO(isCancelled, true, startingNow);
-  }
-  
-  public StateIO startingNow() {
-    return new StateIO(isCancelled, cancellingNow, true);
-  }
-  
-  public StateIO notStartingNow() {
-    return new StateIO(isCancelled, cancellingNow, false);
-  }
-  
-  public boolean isCancelable() {
-    return !isCancelled && !cancellingNow && !startingNow;
-  }
-  
-  public boolean isRunnable() {
-    return !isCancelled && !cancellingNow;
-  }
-}
-
-final class CallStack<T> {
-  
-  private StackItem<T> top = new StackItem<>();
-  
-  public void push() {
-    top.push();
-  }
-
-  public void pop() {
-    if (top.count() > 0) {
-      top.pop();
-    } else {
-      top = top.prev();
-    }
-  }
-  
-  public void add(PartialFunction<? super Throwable, ? extends IO<? extends T>> mapError) {
-    if (top.count() > 0) {
-      top.pop();
-      top = new StackItem<>(top);
-    }
-    top.add(mapError);
-  }
-  
-  public Option<IO<T>> tryHandle(Throwable error) {
-    while (top != null) {
-      top.reset();
-      Option<IO<T>> result = top.tryHandle(error);
-      
-      if (result.isDefined()) {
-        return result;
-      } else {
-        top = top.prev();
-      }
-    }
-    return Option.none();
-  }
-  
-  // XXX: https://www.baeldung.com/java-sneaky-throws
-  @SuppressWarnings("unchecked")
-  public <X extends Throwable, R> R sneakyThrow(Throwable t) throws X {
-    throw (X) t;
-  }
-}
-
-final class StackItem<T> {
-  
-  private int count = 0;
-  private final Deque<PartialFunction<? super Throwable, ? extends IO<? extends T>>> recover = new ArrayDeque<>();
-
-  private final StackItem<T> prev;
-
-  public StackItem() {
-    this(null);
-  }
-
-  public StackItem(StackItem<T> prev) {
-    this.prev = prev;
-  }
-  
-  public StackItem<T> prev() {
-    return prev;
-  }
-  
-  public int count() {
-    return count;
-  }
-  
-  public void push() {
-    count++;
-  }
-  
-  public void pop() {
-    count--;
-  }
-  
-  public void reset() {
-    count = 0;
-  }
-  
-  public void add(PartialFunction<? super Throwable, ? extends IO<? extends T>> mapError) {
-    recover.addFirst(mapError);
-  }
-
-  public Option<IO<T>> tryHandle(Throwable error) {
-    while (!recover.isEmpty()) {
-      var mapError = recover.removeFirst();
-      if (mapError.isDefinedAt(error)) {
-        return Option.some(mapError.andThen(IO::<T>narrowK).apply(error));
-      }
-    }
-    return Option.none();
-  }
-}
-
-interface FutureModule {
-
-  ScheduledExecutorService SCHEDULER = Executors.newScheduledThreadPool(0);
-
-  static Future<Unit> sleep(Executor executor, Duration delay) {
-    return Future.fromCompletableFuture(executor, CompletableFuture.supplyAsync(Unit::unit, delayedExecutor(delay, executor)));
-  }
-
-  static Executor delayedExecutor(Duration delay, Executor executor) {
-    return task -> SCHEDULER.schedule(() -> executor.execute(task), delay.toMillis(), TimeUnit.MILLISECONDS);
-  }
-}
\ No newline at end of file
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java b/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java
deleted file mode 100644
index 5dd2abf..0000000
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/Ref.java
+++ /dev/null
@@ -1,72 +0,0 @@
-/*
- * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
- * Distributed under the terms of the MIT License
- */
-package com.github.tonivade.vavr.effect;
-
-import java.util.Objects;
-import java.util.concurrent.atomic.AtomicReference;
-import java.util.function.UnaryOperator;
-
-import io.vavr.Function1;
-import io.vavr.Tuple2;
-
-public final class Ref<A> {
-
-  private final AtomicReference<A> value;
-
-  private Ref(AtomicReference<A> value) {
-    this.value = Objects.requireNonNull(value);
-  }
-
-  public IO<A> get() {
-    return IO.task(value::get);
-  }
-
-  public IO<Unit> set(A newValue) {
-    return IO.task(() -> { value.set(newValue); return Unit.unit(); });
-  }
-  
-  public <B> IO<B> modify(Function1<A, Tuple2<B, A>> change) {
-    return IO.task(() -> {
-      var loop = true;
-      B result = null;
-      while (loop) {
-        A current = value.get();
-        var tuple = change.apply(current);
-        result = tuple._1();
-        loop = !value.compareAndSet(current, tuple._2());
-      }
-      return result;
-    });
-  }
-
-  public IO<Unit> lazySet(A newValue) {
-    return IO.task(() -> { value.lazySet(newValue); return Unit.unit(); });
-  }
-
-  public IO<A> getAndSet(A newValue) {
-    return IO.task(() -> value.getAndSet(newValue));
-  }
-
-  public IO<A> updateAndGet(UnaryOperator<A> update) {
-    return IO.task(() -> value.updateAndGet(update::apply));
-  }
-
-  public IO<A> getAndUpdate(UnaryOperator<A> update) {
-    return IO.task(() -> value.getAndUpdate(update::apply));
-  }
-  
-  public static <A> IO<Ref<A>> make(A value) {
-    return IO.pure(of(value));
-  }
-
-  public static <A> Ref<A> of(A value) {
-    return new Ref<>(new AtomicReference<>(value));
-  }
-
-  @Override
-  public String toString() {
-    return String.format("Ref(%s)", value.get());
-  }
-}
diff --git a/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java b/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java
deleted file mode 100644
index 11b3583..0000000
--- a/lib/src/main/java/com/github/tonivade/vavr/effect/Unit.java
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
- * Distributed under the terms of the MIT License
- */
-package com.github.tonivade.vavr.effect;
-
-import java.io.Serial;
-import java.io.Serializable;
-
-/**
- * Type that represents a single value called Unit.
- */
-public final class Unit implements Serializable {
-
-  @Serial
-  private static final long serialVersionUID = -8253613036328680583L;
-
-  private static final Unit INSTANCE = new Unit();
-
-  private Unit() {}
-
-  public static Unit unit() {
-    return INSTANCE;
-  }
-
-  @Override
-  public String toString() {
-    return "Unit";
-  }
-  
-  @Serial
-  private Object readResolve() {
-    return INSTANCE;
-  }
-}
diff --git a/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java b/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
deleted file mode 100644
index 59d9477..0000000
--- a/lib/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
+++ /dev/null
@@ -1,394 +0,0 @@
-/*
- * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
- * Distributed under the terms of the MIT License
- */
-package com.github.tonivade.vavr.effect;
-
-import static org.junit.jupiter.api.Assertions.assertAll;
-import static org.junit.jupiter.api.Assertions.assertArrayEquals;
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertThrows;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.timeout;
-import static org.mockito.Mockito.times;
-import static org.mockito.Mockito.verify;
-import static org.mockito.Mockito.when;
-import java.sql.ResultSet;
-import java.sql.SQLException;
-import java.time.Duration;
-import java.util.NoSuchElementException;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.TimeoutException;
-import java.util.function.Consumer;
-import java.util.function.Supplier;
-import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
-import org.mockito.Mock;
-import org.mockito.junit.jupiter.MockitoExtension;
-import io.vavr.CheckedFunction1;
-import io.vavr.Function1;
-import io.vavr.Tuple2;
-import io.vavr.collection.List;
-import io.vavr.collection.Seq;
-import io.vavr.concurrent.Future;
-import io.vavr.control.Either;
-import io.vavr.control.Try;
-
-@ExtendWith(MockitoExtension.class)
-class IOTest {
-
-  @Test
-  void pure() {
-    IO<String> pure = IO.pure("hola mundo");
-
-    assertAll(
-        () -> assertEquals("hola mundo", pure.unsafeRunSync()),
-        () -> assertEquals("HOLA MUNDO", pure.map(String::toUpperCase).unsafeRunSync()),
-        () -> assertArrayEquals(new String[] { "hola", "mundo" },
-            pure.flatMap(string -> IO.task(() -> string.split(" "))).unsafeRunSync()),
-        () -> assertEquals(Integer.valueOf(100), pure.andThen(IO.task(() -> 100)).unsafeRunSync()));
-  }
-  
-  @Test
-  void asyncSuccess() {
-    IO<String> async = IO.async(callback -> {
-      System.out.println(Thread.currentThread().getName());
-      Thread.sleep(100);
-      callback.accept(Try.success("1"));
-    });
-    
-    Future<String> foldMap = IO.forked().andThen(async).runAsync();
-    
-    assertEquals("1", foldMap.get());
-  }
-  
-  @Test
-  void asyncFailure() {
-    IO<String> async = IO.async(callback -> {
-      Thread.sleep(100);
-      callback.accept(Try.failure(new UnsupportedOperationException()));
-    });
-    
-    Future<String> foldMap = IO.forked().andThen(async).runAsync();
-   
-    assertThrows(UnsupportedOperationException.class, foldMap::get);
-  }
-
-//  @Test
-//  void echo() {
-//    IO<Unit> echo = narrowK(console.println("write your name"))
-//        .andThen(narrowK(console.readln()))
-//        .flatMap(name -> narrowK(console.println("Hello " + name)))
-//        .andThen(narrowK(console.println("end")));
-//
-//    ConsoleExecutor executor = new ConsoleExecutor().read("Toni");
-//
-//    executor.run(echo);
-//
-//    assertEquals("write your name\nHello Toni\nend\n", executor.getOutput());
-//  }
-
-  @Test
-  void safeRunAsync() {
-    IO<List<String>> program = currentThreadIO();
-
-    Try<List<String>> result = program.runAsync().await(1, TimeUnit.SECONDS).toTry();
-
-    assertEquals(Try.success(5), result.map(List::size));
-  }
-
-  @Test
-  void bracket() throws SQLException {
-    ResultSet resultSet = mock(ResultSet.class);
-    when(resultSet.getString("id")).thenReturn("value");
-
-    IO<String> bracket = IO.bracket(open(resultSet), IO.liftTry(tryGetString("id")));
-
-    assertEquals("value", bracket.unsafeRunSync());
-    verify(resultSet).close();
-  }
-
-  @Test
-  void safeRunAsyncSuccess(@Mock Consumer<? super Try<? extends String>> callback) {
-    IO.pure("hola").safeRunAsync(callback);
-
-    verify(callback, timeout(1000)).accept(Try.success("hola"));
-  }
-
-  @Test
-  void unsafeRunAsyncFailure(@Mock Consumer<? super Try<? extends String>> callback) {
-    RuntimeException error = new RuntimeException();
-
-    IO.<String>raiseError(error).safeRunAsync(callback);
-
-    verify(callback, timeout(1000)).accept(Try.failure(error));
-  }
-
-  @Test
-  void recover() {
-    IO<String> recover = IO.<String>raiseError(new RuntimeException()).recover(error -> "hola mundo");
-
-    assertEquals("hola mundo", recover.unsafeRunSync());
-  }
-
-  @Test
-  void recoverWith() {
-    IO<String> recover = IO.<String>raiseError(new IllegalArgumentException())
-        .recover(IllegalArgumentException.class, error -> "hola mundo");
-
-    assertEquals("hola mundo", recover.unsafeRunSync());
-  }
-
-  @Test
-  void recoverWithNotMatch() {
-    IO<String> recover = IO.<String>raiseError(new IllegalArgumentException())
-        .recover(NoSuchElementException.class, error -> "hola mundo");
-
-    assertThrows(IllegalArgumentException.class, recover::unsafeRunSync);
-  }
-
-  @Test
-  void retry(@Mock Supplier<String> computation) {
-    when(computation.get()).thenThrow(UnsupportedOperationException.class);
-
-    Try<String> retry = IO.task(computation).retry().safeRunSync();
-
-    assertTrue(retry.isFailure());
-    verify(computation, times(2)).get();
-  }
-
-  @Test
-  void retryFailure(@Mock Supplier<String> computation) {
-    when(computation.get()).thenThrow(UnsupportedOperationException.class);
-
-    Try<String> retry = IO.task(computation).retry(Duration.ofMillis(100), 3).safeRunSync();
-
-    assertTrue(retry.isFailure());
-    verify(computation, times(4)).get();
-  }
-
-  @Test
-  void retrySuccess(@Mock Supplier<String> computation) {
-    when(computation.get())
-        .thenThrow(UnsupportedOperationException.class)
-        .thenThrow(UnsupportedOperationException.class)
-        .thenThrow(UnsupportedOperationException.class)
-        .thenReturn("hola");
-
-    Try<String> retry = IO.task(computation).retry(Duration.ofMillis(100), 3).safeRunSync();
-
-    assertEquals("hola", retry.get());
-    verify(computation, times(4)).get();
-  }
-
-  @Test
-  void repeatSuccess(@Mock Supplier<String> computation) {
-    when(computation.get()).thenReturn("hola");
-
-    Try<String> repeat = IO.task(computation).repeat(Duration.ofMillis(100), 3).safeRunSync();
-
-    assertEquals("hola", repeat.get());
-    verify(computation, times(4)).get();
-  }
-
-  @Test
-  void repeatFailure(@Mock Supplier<String> computation) {
-    when(computation.get()).thenReturn("hola").thenThrow(UnsupportedOperationException.class);
-
-    Try<String> repeat = IO.task(computation).repeat(Duration.ofMillis(100), 3).safeRunSync();
-
-    assertTrue(repeat.isFailure());
-    verify(computation, times(2)).get();
-  }
-
-  @Test
-  void repeat(@Mock Supplier<String> computation) {
-    when(computation.get()).thenReturn("hola");
-
-    Try<String> repeat = IO.task(computation).repeat().safeRunSync();
-
-    assertEquals("hola", repeat.get());
-    verify(computation, times(2)).get();
-  }
-
-  @Test
-  void flatMapped() {
-    IO<String> io = IO.unit()
-        .map(ignore -> "hola")
-        .map(ignore -> "hola")
-        .map(ignore -> "hola")
-        .map(ignore -> "adios");
-
-    assertEquals("adios", io.unsafeRunSync());
-  }
-
-  @Test
-  void stackSafety() {
-    IO<Integer> sum = sum(100000, 0);
-
-    Future<Integer> futureSum = sum.runAsync();
-
-    assertEquals(705082704, sum.unsafeRunSync());
-    assertEquals(Try.success(705082704), futureSum.await(1, TimeUnit.SECONDS).toTry());
-  }
-
-  @Test
-  void timed() {
-    IO<Tuple2<Duration, Integer>> sum = sum(100000, 0).timed();
-
-    Tuple2<Duration, Integer> result = sum.unsafeRunSync();
-
-    assertEquals(705082704, result._2());
-    assertTrue(result._1().toMillis() > 0);
-  }
-  
-  @Test
-  void timeoutFail() {
-    assertThrows(TimeoutException.class, IO.never().timeout(Duration.ofSeconds(1))::unsafeRunSync);
-  }
-  
-  @Test
-  void timeoutSuccess() {
-    assertEquals(1, IO.pure(1).timeout(Duration.ofSeconds(1)).unsafeRunSync());
-  }
-  
-  @Test
-  void traverse() {
-    IO<String> left = IO.task(() -> "left");
-    IO<String> right = IO.task(() -> "right");
-    
-    IO<Seq<String>> traverse = IO.traverse(List.of(left, right));
-    
-    assertEquals(List.of("left", "right"), traverse.unsafeRunSync());
-  }
-
-  @Test
-  void raceA() {
-    IO<Either<Integer, String>> race = IO.race(
-        IO.delay(Duration.ofMillis(10), () -> 10),
-        IO.delay(Duration.ofMillis(100), () -> "b"));
-    
-    Either<Integer, String> orElseThrow = race.unsafeRunSync();
-    
-    assertEquals(Either.left(10), orElseThrow);
-  }
-
-  @Test
-  void raceB() {
-    IO<Either<Integer, String>> race = IO.race(
-        IO.delay(Duration.ofMillis(100), () -> 10),
-        IO.delay(Duration.ofMillis(10), () -> "b"));
-    
-    Either<Integer, String> orElseThrow = race.unsafeRunSync();
-    
-    assertEquals(Either.right("b"), orElseThrow);
-  }
-  
-  @Test
-  void fork() {
-    IO<String> result = IO.pure("hola")
-      .flatMap(hello -> IO.delay(Duration.ofSeconds(1), () -> hello + " toni").fork())
-      .flatMap(Fiber::join);
-    
-    String orElseThrow = result.runAsync().get();
-
-    assertEquals("hola toni", orElseThrow);
-  }
-  
-  @Test
-  void memoize(@Mock Function1<String, String> toUpperCase) {
-    when(toUpperCase.apply(any()))
-      .thenAnswer(args -> args.getArgument(0, String.class).toUpperCase());
-    
-    IO<Function1<String, IO<String>>> memoized = IO.memoize((String str) -> IO.pure(toUpperCase.apply(str)));
-    
-    IO<String> flatMap = memoized.flatMap(x -> x.apply("hola"));
-    flatMap.unsafeRunSync();
-    flatMap.unsafeRunSync();
-    flatMap.unsafeRunSync();
-    flatMap.unsafeRunSync();
-    
-    verify(toUpperCase).apply("hola");
-  }
-  
-  @Test
-  void fibSyncTest() {
-    assertAll(
-        () -> assertEquals(1, fibSync(1).unsafeRunSync()),
-        () -> assertEquals(1, fibSync(2).unsafeRunSync()),
-        () -> assertEquals(2, fibSync(3).unsafeRunSync()),
-        () -> assertEquals(3, fibSync(4).unsafeRunSync()),
-        () -> assertEquals(5, fibSync(5).unsafeRunSync()),
-        () -> assertEquals(8, fibSync(6).unsafeRunSync()),
-        () -> assertEquals(13, fibSync(7).unsafeRunSync()),
-        () -> assertEquals(21, fibSync(8).unsafeRunSync()),
-        () -> assertEquals(55, fibSync(10).unsafeRunSync()),
-        () -> assertEquals(6765, fibSync(20).unsafeRunSync())
-        );
-  }
-  
-  @Test
-  void fibAsyncTest() {
-    assertAll(
-        () -> assertEquals(1, fibAsync(1).unsafeRunSync()),
-        () -> assertEquals(1, fibAsync(2).unsafeRunSync()),
-        () -> assertEquals(2, fibAsync(3).unsafeRunSync()),
-        () -> assertEquals(3, fibAsync(4).unsafeRunSync()),
-        () -> assertEquals(5, fibAsync(5).unsafeRunSync()),
-        () -> assertEquals(8, fibAsync(6).unsafeRunSync()),
-        () -> assertEquals(13, fibAsync(7).unsafeRunSync()),
-        () -> assertEquals(21, fibAsync(8).unsafeRunSync()),
-        () -> assertEquals(55, fibAsync(10).unsafeRunSync()),
-        () -> assertEquals(6765, fibAsync(20).unsafeRunSync())
-        );
-  }
-
-  private IO<Integer> fibSync(int number) {
-    if (number < 2) {
-      return IO.pure(number);
-    }
-    var number1 = fibSync(number - 1);
-    var number2 = fibSync(number - 2);
-    return number1.flatMap(x -> number2.map(y -> x + y));
-  }
-
-  private IO<Integer> fibAsync(int number) {
-    if (number < 2) {
-      return IO.pure(number);
-    }
-    return IO.parMap2(fibAsync(number - 1), fibAsync(number - 2), Integer::sum);
-  }
-
-  private IO<ResultSet> open(ResultSet resultSet) {
-    return IO.pure(resultSet);
-  }
-
-  private Function1<ResultSet, Try<String>> tryGetString(String column) {
-    return rs -> Try.of(() -> getString(column).apply(rs));
-  }
-
-  private CheckedFunction1<ResultSet, String> getString(String column) {
-    return resultSet -> resultSet.getString(column);
-  }
-
-  private IO<Integer> sum(Integer n, Integer sum) {
-    if (n == 0) {
-      return IO.pure(sum);
-    }
-    return IO.suspend(() -> sum(n - 1, sum + n));
-  }
-
-  private IO<List<String>> currentThreadIO() {
-    Ref<List<String>> ref = Ref.of(List.empty());
-    IO<List<String>> currentThread =
-        ref.updateAndGet(list -> list.append(Thread.currentThread().getName()));
-
-    return currentThread
-        .andThen(currentThread
-            .andThen(currentThread
-                .andThen(currentThread
-                    .andThen(currentThread))));
-  }
-}
diff --git a/settings.gradle b/settings.gradle
index 6218084..309d89a 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -1,11 +1 @@
-/*
- * This file was generated by the Gradle 'init' task.
- *
- * The settings file is used to specify which projects to include in your build.
- *
- * Detailed information about configuring a multi-project build in Gradle can be found
- * in the user manual at https://docs.gradle.org/7.4.2/userguide/multi_project_builds.html
- */
-
 rootProject.name = 'vavr-effect'
-include('lib')
diff --git a/src/main/java/com/github/tonivade/vavr/effect/Fiber.java b/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
new file mode 100644
index 0000000..d934c88
--- /dev/null
+++ b/src/main/java/com/github/tonivade/vavr/effect/Fiber.java
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Distributed under the terms of the MIT License
+ */
+package com.github.tonivade.vavr.effect;
+
+public sealed interface Fiber<T> {
+
+  IO<T> join();
+  
+  IO<Unit> cancel();
+  
+  static <T> Fiber<T> of(IO<T> join, IO<Unit> cancel) {
+    return new FiberImpl<>(join, cancel);
+  }
+  
+  record FiberImpl<T>(IO<T> join, IO<Unit> cancel) implements Fiber<T> {}
+}
\ No newline at end of file
diff --git a/src/main/java/com/github/tonivade/vavr/effect/IO.java b/src/main/java/com/github/tonivade/vavr/effect/IO.java
new file mode 100644
index 0000000..aa179af
--- /dev/null
+++ b/src/main/java/com/github/tonivade/vavr/effect/IO.java
@@ -0,0 +1,880 @@
+/*
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Distributed under the terms of the MIT License
+ */
+package com.github.tonivade.vavr.effect;
+
+import static io.vavr.Function1.identity;
+import java.time.Duration;
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.NoSuchElementException;
+import java.util.Objects;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
+import io.vavr.CheckedConsumer;
+import io.vavr.CheckedRunnable;
+import io.vavr.Function1;
+import io.vavr.Function2;
+import io.vavr.PartialFunction;
+import io.vavr.Tuple;
+import io.vavr.Tuple2;
+import io.vavr.collection.HashMap;
+import io.vavr.collection.List;
+import io.vavr.collection.Seq;
+import io.vavr.concurrent.Future;
+import io.vavr.concurrent.Promise;
+import io.vavr.control.Either;
+import io.vavr.control.Option;
+import io.vavr.control.Try;
+
+public sealed interface IO<T> {
+
+  IO<Unit> UNIT = pure(Unit.unit());
+
+  default Future<T> runAsync() {
+    return runAsync(this, IOConnection.UNCANCELLABLE).future();
+  }
+
+  default Future<T> runAsync(Executor executor) {
+    return forked(executor).andThen(this).runAsync();
+  }
+  
+  default T unsafeRunSync() {
+    return safeRunSync().get();
+  }
+
+  default Try<T> safeRunSync() {
+    return runAsync().toTry();
+  }
+
+  default void safeRunAsync(Consumer<? super Try<? extends T>> callback) {
+    safeRunAsync(Future.DEFAULT_EXECUTOR, callback);
+  }
+
+  default void safeRunAsync(Executor executor, Consumer<? super Try<? extends T>> callback) {
+    runAsync(executor).onComplete(callback);
+  }
+
+  default <R> IO<R> map(Function1<? super T, ? extends R> map) {
+    return flatMap(map.andThen(IO::pure));
+  }
+
+  default <R> IO<R> flatMap(Function1<? super T, ? extends IO<? extends R>> map) {
+    return new FlatMapped<>(this, map.andThen(IO::narrowK));
+  }
+
+  default <R> IO<R> andThen(IO<? extends R> after) {
+    return flatMap(ignore -> after);
+  }
+
+  default <R> IO<R> ap(IO<Function1<? super T, ? extends R>> apply) {
+    return parMap2(Future.DEFAULT_EXECUTOR, this, apply, (v, a) -> a.apply(v));
+  }
+
+  default IO<Try<T>> attempt() {
+    return map(Try::success).recover(Try::failure);
+  }
+
+  default IO<Either<Throwable, T>> either() {
+    return attempt().map(Try::toEither);
+  }
+
+  default <L, R> IO<Either<L, R>> either(Function1<? super Throwable, ? extends L> mapError,
+                                         Function1<? super T, ? extends R> mapper) {
+    return either().map(either -> either.bimap(mapError, mapper));
+  }
+
+  default <R> IO<R> redeem(Function1<? super Throwable, ? extends R> mapError,
+                           Function1<? super T, ? extends R> mapper) {
+    return attempt().map(result -> result.fold(mapError, mapper));
+  }
+
+  default <R> IO<R> redeemWith(Function1<? super Throwable, IO<? extends R>> mapError,
+                               Function1<? super T, IO<? extends R>> mapper) {
+    return attempt().flatMap(result -> result.fold(mapError, mapper));
+  }
+
+  default IO<T> recover(Function1<? super Throwable, ? extends T> mapError) {
+    return recoverWith(partialFunction(x -> true, mapError.andThen(IO::pure)));
+  }
+
+  @SuppressWarnings("unchecked")
+  default <X extends Throwable> IO<T> recover(Class<X> type, Function1<? super X, ? extends T> function) {
+    return recoverWith(partialFunction(error -> error.getClass().equals(type), t -> function.andThen(IO::pure).apply((X) t)));
+  }
+  
+  @SuppressWarnings("serial")
+  static <A, B> PartialFunction<A, B> partialFunction(Predicate<? super A> matcher, Function1<? super A, ? extends B> function) {
+    return new PartialFunction<>() {
+      
+      @Override
+      public boolean isDefinedAt(A value) {
+        return matcher.test(value);
+      }
+      
+      @Override
+      public B apply(A t) {
+        return function.apply(t);
+      }
+    };
+  }
+
+  default IO<T> recoverWith(PartialFunction<? super Throwable, IO<? extends T>> mapper) {
+    return new Recover<>(this, mapper);
+  }
+
+  default IO<Tuple2<Duration, T>> timed() {
+    return IO.task(System::nanoTime).flatMap(
+      start -> map(result -> Tuple.of(Duration.ofNanos(System.nanoTime() - start), result)));
+  }
+  
+  default IO<Fiber<T>> fork() {
+    return async(callback -> {
+      IOConnection connection = IOConnection.cancellable();
+      Promise<T> promise = runAsync(this, connection);
+      
+      IO<T> join = fromFuture(promise.future());
+      IO<Unit> cancel = exec(connection::cancel);
+      
+      callback.accept(Try.success(Fiber.of(join, cancel)));
+    });
+  }
+
+  default IO<T> timeout(Duration duration) {
+    return timeout(Future.DEFAULT_EXECUTOR, duration);
+  }
+  
+  default IO<T> timeout(Executor executor, Duration duration) {
+    return racePair(executor, this, sleep(duration)).flatMap(either -> either.fold(
+        ta -> ta._2().cancel().map(x -> ta._1()),
+        tb -> tb._1().cancel().flatMap(x -> IO.raiseError(new TimeoutException()))));
+  }
+
+  default IO<T> repeat() {
+    return repeat(1);
+  }
+
+  default IO<T> repeat(int times) {
+    return repeat(this, unit(), times);
+  }
+
+  default IO<T> repeat(Duration delay) {
+    return repeat(delay, 1);
+  }
+
+  default IO<T> repeat(Duration delay, int times) {
+    return repeat(this, sleep(delay), times);
+  }
+
+  default IO<T> retry() {
+    return retry(1);
+  }
+
+  default IO<T> retry(int maxRetries) {
+    return retry(this, unit(), maxRetries);
+  }
+
+  default IO<T> retry(Duration delay) {
+    return retry(delay, 1);
+  }
+
+  default IO<T> retry(Duration delay, int maxRetries) {
+    return retry(this, sleep(delay), maxRetries);
+  }
+
+  @SuppressWarnings("unchecked")
+  static <T> IO<T> narrowK(IO<? extends T> value) {
+    return (IO<T>) value;
+  }
+
+  static <T> IO<T> pure(T value) {
+    return new Pure<>(value);
+  }
+  
+  static <A, B> IO<Either<A, B>> race(IO<? extends A> fa, IO<? extends B> fb) {
+    return race(Future.DEFAULT_EXECUTOR, fa, fb);
+  }
+  
+  static <A, B> IO<Either<A, B>> race(Executor executor, IO<? extends A> fa, IO<? extends B> fb) {
+    return racePair(executor, fa, fb).flatMap(either -> either.fold(
+        ta -> ta._2().cancel().map(x -> Either.left(ta._1())),
+        tb -> tb._1().cancel().map(x -> Either.right(tb._2()))));
+  }
+  
+  static <A, B> IO<Either<Tuple2<A, Fiber<B>>, Tuple2<Fiber<A>, B>>> racePair(Executor executor, IO<? extends A> fa, IO<? extends B> fb) {
+    return cancellable(callback -> {
+      
+      IOConnection connection1 = IOConnection.cancellable();
+      IOConnection connection2 = IOConnection.cancellable();
+      
+      Promise<A> promiseA = runAsync(IO.forked(executor).andThen(fa), connection1);
+      Promise<B> promiseB = runAsync(IO.forked(executor).andThen(fb), connection2);
+
+      promiseA.future().onComplete(result -> callback.accept(
+          result.map(a -> Either.left(Tuple.of(a, Fiber.of(IO.fromFuture(promiseB.future()), IO.exec(connection2::cancel)))))));
+      promiseB.future().onComplete(result -> callback.accept(
+          result.map(b -> Either.right(Tuple.of(Fiber.of(IO.fromFuture(promiseA.future()), IO.exec(connection2::cancel)), b)))));
+
+      return IO.exec(() -> {
+        try {
+          connection1.cancel();
+        } finally {
+          connection2.cancel();
+        }
+      });
+    });
+  }
+
+  static <T> IO<T> raiseError(Throwable error) {
+    return new Failure<>(error);
+  }
+
+  static <T> IO<T> delay(Duration delay, Supplier<? extends T> lazy) {
+    return sleep(delay).andThen(task(lazy));
+  }
+
+  static <T> IO<T> suspend(Supplier<IO<? extends T>> lazy) {
+    return new Suspend<>(lazy);
+  }
+
+  static <T, R> Function1<T, IO<R>> lift(Function1<T, R> task) {
+    return task.andThen(IO::pure);
+  }
+
+  public static <A, B> Function1<A, IO<B>> liftOption(Function1<? super A, ? extends Option<? extends B>> function) {
+    return value -> fromOption(function.apply(value));
+  }
+
+  public static <A, B> Function1<A, IO<B>> liftTry(Function1<? super A, ? extends Try<? extends B>> function) {
+    return value -> fromTry(function.apply(value));
+  }
+
+  public static <A, B> Function1<A, IO<B>> liftEither(Function1<? super A, ? extends Either<Throwable, ? extends B>> function) {
+    return value -> fromEither(function.apply(value));
+  }
+
+  static <T> IO<T> fromOption(Option<? extends T> task) {
+    return fromEither(toEither(task));
+  }
+
+  static <T> IO<T> fromTry(Try<? extends T> task) {
+    return fromEither(task.toEither());
+  }
+
+  static <T> IO<T> fromEither(Either<Throwable, ? extends T> task) {
+    return task.fold(IO::raiseError, IO::pure);
+  }
+  
+  static <T> IO<T> fromFuture(Future<? extends T> promise) {
+    CheckedConsumer<Consumer<? super Try<? extends T>>> callback = promise::onComplete;
+    return async(callback);
+  }
+  
+  static <T> IO<T> fromCompletableFuture(CompletableFuture<? extends T> promise) {
+    return fromFuture(Future.fromCompletableFuture(promise));
+  }
+
+  static IO<Unit> sleep(Duration duration) {
+    return sleep(Future.DEFAULT_EXECUTOR, duration);
+  }
+
+  static IO<Unit> sleep(Executor executor, Duration duration) {
+    return cancellable(callback -> {
+      Future<Unit> sleep = FutureModule.sleep(executor,duration)
+        .onComplete(result -> callback.accept(Try.success(Unit.unit())));
+      return IO.exec(() -> sleep.cancel(true));
+    });
+  }
+
+  static IO<Unit> exec(CheckedRunnable task) {
+    return task(asSupplier(task));
+  }
+
+  static <T> IO<T> task(Supplier<? extends T> producer) {
+    return new Delay<>(producer);
+  }
+
+  static <T> IO<T> never() {
+    return async(callback -> {});
+  }
+  
+  static IO<Unit> forked() {
+    return forked(Future.DEFAULT_EXECUTOR);
+  }
+  
+  static IO<Unit> forked(Executor executor) {
+    return async(callback -> executor.execute(() -> callback.accept(Try.success(Unit.unit()))));
+  }
+
+  static <T> IO<T> async(CheckedConsumer<Consumer<? super Try<? extends T>>> callback) {
+    return cancellable(asFunction(callback));
+  }
+
+  static <T> IO<T> cancellable(Function1<Consumer<? super Try<? extends T>>, IO<Unit>> callback) {
+    return new Async<>(callback);
+  }
+
+  static <A, T> IO<Function1<A, IO<T>>> memoize(Function1<A, IO<T>> function) {
+    return memoize(Future.DEFAULT_EXECUTOR, function);
+  }
+
+  static <A, T> IO<Function1<A, IO<T>>> memoize(Executor executor, Function1<A, IO<T>> function) {
+    var ref = Ref.make(HashMap.<A, Promise<T>>empty());
+    return ref.map(r -> {
+      Function1<A, IO<IO<T>>> result = a -> r.modify(map -> map.get(a).fold(() -> {
+        Promise<T> promise = Promise.make();
+        function.apply(a).safeRunAsync(executor, promise::tryComplete);
+        return Tuple.of(IO.fromFuture(promise.future()), map.put(a, promise));
+      }, promise -> Tuple.of(IO.fromFuture(promise.future()), map)));
+      return result.andThen(io -> io.flatMap(identity()));
+    });
+  }
+
+  static IO<Unit> unit() {
+    return UNIT;
+  }
+
+  static <T, R> IO<R> bracket(IO<? extends T> acquire, 
+      Function1<? super T, ? extends IO<? extends R>> use, Function1<? super T, IO<Unit>> release) {
+    return cancellable(callback -> {
+      
+      IOConnection cancellable = IOConnection.cancellable();
+      
+      Promise<? extends T> promise = runAsync(acquire, cancellable);
+      
+      promise.future()
+        .onFailure(error -> callback.accept(Try.failure(error)))
+        .onSuccess(resource -> runAsync(use.andThen(IO::narrowK).apply(resource), cancellable).future()
+          .onComplete(result -> runAsync(release.andThen(IO::narrowK).apply(resource), cancellable).future()
+            .onComplete(ignore -> callback.accept(result))
+        ));
+      
+      return IO.exec(cancellable::cancel);
+    });
+  }
+
+  static <T, R> IO<R> bracket(IO<? extends T> acquire, 
+      Function1<? super T, ? extends IO<? extends R>> use, CheckedConsumer<? super T> release) {
+    return bracket(acquire, use, asFunction(release));
+  }
+
+  static <T extends AutoCloseable, R> IO<R> bracket(IO<? extends T> acquire, 
+      Function1<? super T, ? extends IO<? extends R>> use) {
+    return bracket(acquire, use, AutoCloseable::close);
+  }
+
+  static IO<Unit> sequence(Seq<IO<?>> sequence) {
+    IO<?> initial = IO.unit();
+    return sequence.foldLeft(initial, (IO<?> a, IO<?> b) -> a.andThen(b)).andThen(IO.unit());
+  }
+
+  static <A> IO<Seq<A>> traverse(Seq<IO<A>> sequence) {
+    return traverse(Future.DEFAULT_EXECUTOR, sequence);
+  }
+
+  static <A> IO<Seq<A>> traverse(Executor executor, Seq<IO<A>> sequence) {
+    return sequence.foldLeft(pure(List.empty()), 
+        (IO<Seq<A>> xs, IO<A> a) -> parMap2(executor, xs, a, Seq::append));
+  }
+
+  static <A, B, C> IO<C> parMap2(IO<? extends A> fa, IO<? extends B> fb,
+                              Function2<? super A, ? super B, ? extends C> mapper) {
+    return parMap2(Future.DEFAULT_EXECUTOR, fa, fb, mapper);
+  }
+
+  static <A, B, C> IO<C> parMap2(Executor executor, IO<? extends A> fa, IO<? extends B> fb,
+                              Function2<? super A, ? super B, ? extends C> mapper) {
+    return cancellable(callback -> {
+      
+      IOConnection connection1 = IOConnection.cancellable();
+      IOConnection connection2 = IOConnection.cancellable();
+      
+      Promise<A> promiseA = runAsync(IO.forked(executor).andThen(fa), connection1);
+      Promise<B> promiseB = runAsync(IO.forked(executor).andThen(fb), connection2);
+      
+      promiseA.future().onComplete(a -> promiseB.future().onComplete(b -> callback.accept(map2(a, b, mapper))));
+      
+      return IO.exec(() -> {
+        try {
+          connection1.cancel();
+        } finally {
+          connection2.cancel();
+        }
+      });
+    });
+  }
+
+  static <A, B> IO<Tuple2<A, B>> tuple(IO<? extends A> fa, IO<? extends B> fb) {
+    return tuple(Future.DEFAULT_EXECUTOR, fa, fb);
+  }
+
+  static <A, B> IO<Tuple2<A, B>> tuple(Executor executor, IO<? extends A> fa, IO<? extends B> fb) {
+    return parMap2(executor, fa, fb, Tuple::of);
+  }
+
+  private static <T> Promise<T> runAsync(IO<T> current, IOConnection connection) {
+    return runAsync(current, connection, new CallStack<>(), Promise.make());
+  }
+
+  private static <A, B, C> Try<? extends C> map2(Try<A> a, Try<B> b, Function2<? super A, ? super B, ? extends C> mapper) {
+    return a.flatMap(x -> b.map(y -> mapper.apply(x, y)));
+  }
+
+  private static <T> Either<Throwable, T> toEither(Option<? extends T> task) {
+    return task.fold(() -> Either.left(new NoSuchElementException()), Either::right);
+  }
+
+  private static Supplier<Unit> asSupplier(CheckedRunnable task) {
+    return () -> {
+      task.unchecked().run();
+      return Unit.unit();
+    };
+  }
+
+  private static <T> Function1<T, IO<Unit>> asFunction(CheckedConsumer<? super T> release) {
+    return t -> {
+      release.unchecked().accept(t);
+      return unit();
+    };
+  }
+
+  @SuppressWarnings("unchecked")
+  private static <T, U, V> Promise<T> runAsync(IO<T> current, IOConnection connection, CallStack<T> stack, Promise<T> promise) {
+    while (true) {
+      try {
+        current = unwrap(current, stack, identity());
+        
+        if (current instanceof Pure<T> pure) {
+          return promise.success(pure.value);
+        }
+        
+        if (current instanceof Async<T> async) {
+          return executeAsync(async, connection, promise);
+        }
+        
+        if (current instanceof FlatMapped) {
+          stack.push();
+
+          var flatMapped = (FlatMapped<U, T>) current;
+          IO<U> source = IO.narrowK(unwrap(flatMapped.current, stack, u -> u.flatMap(flatMapped.next)));
+          
+          if (source instanceof Async<U> async) {
+            Promise<U> nextPromise = Promise.make();
+            
+            nextPromise.future().andThen(tryU -> tryU.onFailure(promise::failure)
+                .onSuccess(u -> runAsync(IO.narrowK(flatMapped.next.apply(u)), connection, stack, promise)));
+            
+            executeAsync(async, connection, nextPromise);
+            
+            return promise;
+          }
+
+          if (source instanceof Pure<U> pure) {
+            Function1<? super U, IO<T>> andThen = flatMapped.next.andThen(IO::narrowK);
+            current = andThen.apply(pure.value);
+          } else if (source instanceof FlatMapped) {
+            FlatMapped<V, U> flatMapped2 = (FlatMapped<V, U>) source;
+            current = flatMapped2.current.flatMap(a -> flatMapped2.next.apply(a).flatMap(flatMapped.next));
+          }
+        } else {
+          stack.pop();
+        }
+      } catch (Throwable error) {
+        Option<IO<T>> result = stack.tryHandle(error);
+        
+        if (result.isDefined()) {
+          current = result.get();
+        } else {
+          return promise.failure(error);
+        }
+      }
+    }
+  }
+
+  private static <T, U> IO<T> unwrap(IO<T> current, CallStack<U> stack, Function1<IO<? extends T>, IO<? extends U>> next) {
+    while (true) {
+      if (current instanceof Failure<T> failure) {
+        return stack.sneakyThrow(failure.error);
+      } else if (current instanceof Recover<T> recover) {
+        stack.add(partialFunction(recover.mapper::isDefinedAt, recover.mapper.andThen(next)));
+        current = recover.current;
+      } else if (current instanceof Suspend<T> suspend) {
+        Supplier<IO<T>> andThen = () -> IO.narrowK(suspend.lazy.get());
+        current = andThen.get();
+      } else if (current instanceof Delay<T> delay) {
+        return IO.pure(delay.task.get());
+      } else if (current instanceof Pure) {
+        return current;
+      } else if (current instanceof FlatMapped) {
+        return current;
+      } else if (current instanceof Async) {
+        return current;
+      } else {
+        throw new IllegalStateException();
+      }
+    }
+  }
+
+  private static <T> Promise<T> executeAsync(Async<T> current, IOConnection connection, Promise<T> promise) {
+    if (connection.isCancellable() && !connection.updateState(StateIO::startingNow).isRunnable()) {
+      return promise.complete(Try.failure(new CancellationException()));
+    }
+    
+    connection.setCancelToken(current.callback.apply(promise::tryComplete));
+    
+    promise.future().andThen(x -> connection.setCancelToken(UNIT));
+    
+    if (connection.isCancellable() && connection.updateState(StateIO::notStartingNow).isCancellingNow()) {
+      connection.cancelNow();
+    }
+
+    return promise;
+  }
+
+  private static <T> IO<T> repeat(IO<T> self, IO<Unit> pause, int times) {
+    return self.redeemWith(IO::raiseError, value -> {
+      if (times > 0) {
+        return pause.andThen(repeat(self, pause, times - 1));
+      } else return IO.pure(value);
+    });
+  }
+
+  private static <T> IO<T> retry(IO<T> self, IO<Unit> pause, int maxRetries) {
+    return self.redeemWith(error -> {
+      if (maxRetries > 0) {
+        return pause.andThen(retry(self, pause.repeat(), maxRetries - 1));
+      } else return IO.raiseError(error);
+    }, IO::pure);
+  }
+
+  final class Pure<T> implements IO<T> {
+
+    private final T value;
+
+    private Pure(T value) {
+      this.value = Objects.requireNonNull(value);
+    }
+
+    @Override
+    public String toString() {
+      return "Pure(" + value + ")";
+    }
+  }
+
+  final class Failure<T> implements IO<T> {
+
+    private final Throwable error;
+
+    private Failure(Throwable error) {
+      this.error = Objects.requireNonNull(error);
+    }
+
+    @Override
+    public String toString() {
+      return "Failure(" + error + ")";
+    }
+  }
+
+  final class FlatMapped<T, R> implements IO<R> {
+
+    private final IO<? extends T> current;
+    private final Function1<? super T, ? extends IO<? extends R>> next;
+
+    private FlatMapped(IO<? extends T> current,
+                         Function1<? super T, ? extends IO<? extends R>> next) {
+      this.current = Objects.requireNonNull(current);
+      this.next = Objects.requireNonNull(next);
+    }
+
+    @Override
+    public String toString() {
+      return "FlatMapped(" + current + ", ?)";
+    }
+  }
+
+  final class Delay<T> implements IO<T> {
+
+    private final Supplier<? extends T> task;
+
+    private Delay(Supplier<? extends T> task) {
+      this.task = Objects.requireNonNull(task);
+    }
+
+    @Override
+    public String toString() {
+      return "Delay(?)";
+    }
+  }
+
+  final class Async<T> implements IO<T> {
+
+    private final Function1<Consumer<? super Try<? extends T>>, IO<Unit>> callback;
+
+    private Async(Function1<Consumer<? super Try<? extends T>>, IO<Unit>> callback) {
+      this.callback = Objects.requireNonNull(callback);
+    }
+
+    @Override
+    public String toString() {
+      return "Async(?)";
+    }
+  }
+
+  final class Suspend<T> implements IO<T> {
+
+    private final Supplier<? extends IO<? extends T>> lazy;
+
+    private Suspend(Supplier<? extends IO<? extends T>> lazy) {
+      this.lazy = Objects.requireNonNull(lazy);
+    }
+
+    @Override
+    public String toString() {
+      return "Suspend(?)";
+    }
+  }
+
+  final class Recover<T> implements IO<T> {
+
+    private final IO<T> current;
+    private final PartialFunction<? super Throwable, ? extends IO<? extends T>> mapper;
+
+    private Recover(IO<T> current, PartialFunction<? super Throwable, ? extends IO<? extends T>> mapper) {
+      this.current = Objects.requireNonNull(current);
+      this.mapper = Objects.requireNonNull(mapper);
+    }
+
+    @Override
+    public String toString() {
+      return "Recover(" + current + ", ?)";
+    }
+  }
+}
+
+interface IOConnection {
+  
+  IOConnection UNCANCELLABLE = new IOConnection() {
+    @Override
+    public boolean isCancellable() { return false; }
+
+    @Override
+    public void setCancelToken(IO<Unit> cancel) { }
+
+    @Override
+    public void cancelNow() { }
+
+    @Override
+    public void cancel() { }
+
+    @Override
+    public StateIO updateState(UnaryOperator<StateIO> update) { return StateIO.INITIAL; }
+  };
+  
+  boolean isCancellable();
+
+  void setCancelToken(IO<Unit> cancel);
+  
+  void cancelNow();
+  
+  void cancel();
+  
+  StateIO updateState(UnaryOperator<StateIO> update);
+  
+  static IOConnection cancellable() {
+    return new IOConnection() {
+      
+      private IO<Unit> cancelToken;
+      private final AtomicReference<StateIO> state = new AtomicReference<>(StateIO.INITIAL);
+      
+      @Override
+      public boolean isCancellable() { return true; }
+      
+      @Override
+      public void setCancelToken(IO<Unit> cancel) { this.cancelToken = Objects.requireNonNull(cancel); }
+      
+      @Override
+      public void cancelNow() { cancelToken.runAsync(); }
+      
+      @Override
+      public void cancel() {
+        if (state.getAndUpdate(StateIO::cancellingNow).isCancelable()) {
+          cancelNow();
+        
+          state.set(StateIO.CANCELLED);
+        }
+      }
+      
+      @Override
+      public StateIO updateState(UnaryOperator<StateIO> update) {
+        return state.updateAndGet(update::apply);
+      }
+    };
+  }
+}
+
+final class StateIO {
+  
+  public static final StateIO INITIAL = new StateIO(false, false, false);
+  public static final StateIO CANCELLED = new StateIO(true, false, false);
+  
+  private final boolean isCancelled;
+  private final boolean cancellingNow;
+  private final boolean startingNow;
+  
+  public StateIO(boolean isCancelled, boolean cancellingNow, boolean startingNow) {
+    this.isCancelled = isCancelled;
+    this.cancellingNow = cancellingNow;
+    this.startingNow = startingNow;
+  }
+  
+  public boolean isCancelled() {
+    return isCancelled;
+  }
+  
+  public boolean isCancellingNow() {
+    return cancellingNow;
+  }
+  
+  public boolean isStartingNow() {
+    return startingNow;
+  }
+  
+  public StateIO cancellingNow() {
+    return new StateIO(isCancelled, true, startingNow);
+  }
+  
+  public StateIO startingNow() {
+    return new StateIO(isCancelled, cancellingNow, true);
+  }
+  
+  public StateIO notStartingNow() {
+    return new StateIO(isCancelled, cancellingNow, false);
+  }
+  
+  public boolean isCancelable() {
+    return !isCancelled && !cancellingNow && !startingNow;
+  }
+  
+  public boolean isRunnable() {
+    return !isCancelled && !cancellingNow;
+  }
+}
+
+final class CallStack<T> {
+  
+  private StackItem<T> top = new StackItem<>();
+  
+  public void push() {
+    top.push();
+  }
+
+  public void pop() {
+    if (top.count() > 0) {
+      top.pop();
+    } else {
+      top = top.prev();
+    }
+  }
+  
+  public void add(PartialFunction<? super Throwable, ? extends IO<? extends T>> mapError) {
+    if (top.count() > 0) {
+      top.pop();
+      top = new StackItem<>(top);
+    }
+    top.add(mapError);
+  }
+  
+  public Option<IO<T>> tryHandle(Throwable error) {
+    while (top != null) {
+      top.reset();
+      Option<IO<T>> result = top.tryHandle(error);
+      
+      if (result.isDefined()) {
+        return result;
+      } else {
+        top = top.prev();
+      }
+    }
+    return Option.none();
+  }
+  
+  // XXX: https://www.baeldung.com/java-sneaky-throws
+  @SuppressWarnings("unchecked")
+  public <X extends Throwable, R> R sneakyThrow(Throwable t) throws X {
+    throw (X) t;
+  }
+}
+
+final class StackItem<T> {
+  
+  private int count = 0;
+  private final Deque<PartialFunction<? super Throwable, ? extends IO<? extends T>>> recover = new ArrayDeque<>();
+
+  private final StackItem<T> prev;
+
+  public StackItem() {
+    this(null);
+  }
+
+  public StackItem(StackItem<T> prev) {
+    this.prev = prev;
+  }
+  
+  public StackItem<T> prev() {
+    return prev;
+  }
+  
+  public int count() {
+    return count;
+  }
+  
+  public void push() {
+    count++;
+  }
+  
+  public void pop() {
+    count--;
+  }
+  
+  public void reset() {
+    count = 0;
+  }
+  
+  public void add(PartialFunction<? super Throwable, ? extends IO<? extends T>> mapError) {
+    recover.addFirst(mapError);
+  }
+
+  public Option<IO<T>> tryHandle(Throwable error) {
+    while (!recover.isEmpty()) {
+      var mapError = recover.removeFirst();
+      if (mapError.isDefinedAt(error)) {
+        return Option.some(mapError.andThen(IO::<T>narrowK).apply(error));
+      }
+    }
+    return Option.none();
+  }
+}
+
+interface FutureModule {
+
+  ScheduledExecutorService SCHEDULER = Executors.newScheduledThreadPool(0);
+
+  static Future<Unit> sleep(Executor executor, Duration delay) {
+    return Future.fromCompletableFuture(executor, CompletableFuture.supplyAsync(Unit::unit, delayedExecutor(delay, executor)));
+  }
+
+  static Executor delayedExecutor(Duration delay, Executor executor) {
+    return task -> SCHEDULER.schedule(() -> executor.execute(task), delay.toMillis(), TimeUnit.MILLISECONDS);
+  }
+}
\ No newline at end of file
diff --git a/src/main/java/com/github/tonivade/vavr/effect/Ref.java b/src/main/java/com/github/tonivade/vavr/effect/Ref.java
new file mode 100644
index 0000000..5dd2abf
--- /dev/null
+++ b/src/main/java/com/github/tonivade/vavr/effect/Ref.java
@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Distributed under the terms of the MIT License
+ */
+package com.github.tonivade.vavr.effect;
+
+import java.util.Objects;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.UnaryOperator;
+
+import io.vavr.Function1;
+import io.vavr.Tuple2;
+
+public final class Ref<A> {
+
+  private final AtomicReference<A> value;
+
+  private Ref(AtomicReference<A> value) {
+    this.value = Objects.requireNonNull(value);
+  }
+
+  public IO<A> get() {
+    return IO.task(value::get);
+  }
+
+  public IO<Unit> set(A newValue) {
+    return IO.task(() -> { value.set(newValue); return Unit.unit(); });
+  }
+  
+  public <B> IO<B> modify(Function1<A, Tuple2<B, A>> change) {
+    return IO.task(() -> {
+      var loop = true;
+      B result = null;
+      while (loop) {
+        A current = value.get();
+        var tuple = change.apply(current);
+        result = tuple._1();
+        loop = !value.compareAndSet(current, tuple._2());
+      }
+      return result;
+    });
+  }
+
+  public IO<Unit> lazySet(A newValue) {
+    return IO.task(() -> { value.lazySet(newValue); return Unit.unit(); });
+  }
+
+  public IO<A> getAndSet(A newValue) {
+    return IO.task(() -> value.getAndSet(newValue));
+  }
+
+  public IO<A> updateAndGet(UnaryOperator<A> update) {
+    return IO.task(() -> value.updateAndGet(update::apply));
+  }
+
+  public IO<A> getAndUpdate(UnaryOperator<A> update) {
+    return IO.task(() -> value.getAndUpdate(update::apply));
+  }
+  
+  public static <A> IO<Ref<A>> make(A value) {
+    return IO.pure(of(value));
+  }
+
+  public static <A> Ref<A> of(A value) {
+    return new Ref<>(new AtomicReference<>(value));
+  }
+
+  @Override
+  public String toString() {
+    return String.format("Ref(%s)", value.get());
+  }
+}
diff --git a/src/main/java/com/github/tonivade/vavr/effect/Unit.java b/src/main/java/com/github/tonivade/vavr/effect/Unit.java
new file mode 100644
index 0000000..11b3583
--- /dev/null
+++ b/src/main/java/com/github/tonivade/vavr/effect/Unit.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Distributed under the terms of the MIT License
+ */
+package com.github.tonivade.vavr.effect;
+
+import java.io.Serial;
+import java.io.Serializable;
+
+/**
+ * Type that represents a single value called Unit.
+ */
+public final class Unit implements Serializable {
+
+  @Serial
+  private static final long serialVersionUID = -8253613036328680583L;
+
+  private static final Unit INSTANCE = new Unit();
+
+  private Unit() {}
+
+  public static Unit unit() {
+    return INSTANCE;
+  }
+
+  @Override
+  public String toString() {
+    return "Unit";
+  }
+  
+  @Serial
+  private Object readResolve() {
+    return INSTANCE;
+  }
+}
diff --git a/src/test/java/com/github/tonivade/vavr/effect/IOTest.java b/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
new file mode 100644
index 0000000..59d9477
--- /dev/null
+++ b/src/test/java/com/github/tonivade/vavr/effect/IOTest.java
@@ -0,0 +1,394 @@
+/*
+ * Copyright (c) 2022, Antonio Gabriel Muñoz Conejo <antoniogmc at gmail dot com>
+ * Distributed under the terms of the MIT License
+ */
+package com.github.tonivade.vavr.effect;
+
+import static org.junit.jupiter.api.Assertions.assertAll;
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.timeout;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.time.Duration;
+import java.util.NoSuchElementException;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import io.vavr.CheckedFunction1;
+import io.vavr.Function1;
+import io.vavr.Tuple2;
+import io.vavr.collection.List;
+import io.vavr.collection.Seq;
+import io.vavr.concurrent.Future;
+import io.vavr.control.Either;
+import io.vavr.control.Try;
+
+@ExtendWith(MockitoExtension.class)
+class IOTest {
+
+  @Test
+  void pure() {
+    IO<String> pure = IO.pure("hola mundo");
+
+    assertAll(
+        () -> assertEquals("hola mundo", pure.unsafeRunSync()),
+        () -> assertEquals("HOLA MUNDO", pure.map(String::toUpperCase).unsafeRunSync()),
+        () -> assertArrayEquals(new String[] { "hola", "mundo" },
+            pure.flatMap(string -> IO.task(() -> string.split(" "))).unsafeRunSync()),
+        () -> assertEquals(Integer.valueOf(100), pure.andThen(IO.task(() -> 100)).unsafeRunSync()));
+  }
+  
+  @Test
+  void asyncSuccess() {
+    IO<String> async = IO.async(callback -> {
+      System.out.println(Thread.currentThread().getName());
+      Thread.sleep(100);
+      callback.accept(Try.success("1"));
+    });
+    
+    Future<String> foldMap = IO.forked().andThen(async).runAsync();
+    
+    assertEquals("1", foldMap.get());
+  }
+  
+  @Test
+  void asyncFailure() {
+    IO<String> async = IO.async(callback -> {
+      Thread.sleep(100);
+      callback.accept(Try.failure(new UnsupportedOperationException()));
+    });
+    
+    Future<String> foldMap = IO.forked().andThen(async).runAsync();
+   
+    assertThrows(UnsupportedOperationException.class, foldMap::get);
+  }
+
+//  @Test
+//  void echo() {
+//    IO<Unit> echo = narrowK(console.println("write your name"))
+//        .andThen(narrowK(console.readln()))
+//        .flatMap(name -> narrowK(console.println("Hello " + name)))
+//        .andThen(narrowK(console.println("end")));
+//
+//    ConsoleExecutor executor = new ConsoleExecutor().read("Toni");
+//
+//    executor.run(echo);
+//
+//    assertEquals("write your name\nHello Toni\nend\n", executor.getOutput());
+//  }
+
+  @Test
+  void safeRunAsync() {
+    IO<List<String>> program = currentThreadIO();
+
+    Try<List<String>> result = program.runAsync().await(1, TimeUnit.SECONDS).toTry();
+
+    assertEquals(Try.success(5), result.map(List::size));
+  }
+
+  @Test
+  void bracket() throws SQLException {
+    ResultSet resultSet = mock(ResultSet.class);
+    when(resultSet.getString("id")).thenReturn("value");
+
+    IO<String> bracket = IO.bracket(open(resultSet), IO.liftTry(tryGetString("id")));
+
+    assertEquals("value", bracket.unsafeRunSync());
+    verify(resultSet).close();
+  }
+
+  @Test
+  void safeRunAsyncSuccess(@Mock Consumer<? super Try<? extends String>> callback) {
+    IO.pure("hola").safeRunAsync(callback);
+
+    verify(callback, timeout(1000)).accept(Try.success("hola"));
+  }
+
+  @Test
+  void unsafeRunAsyncFailure(@Mock Consumer<? super Try<? extends String>> callback) {
+    RuntimeException error = new RuntimeException();
+
+    IO.<String>raiseError(error).safeRunAsync(callback);
+
+    verify(callback, timeout(1000)).accept(Try.failure(error));
+  }
+
+  @Test
+  void recover() {
+    IO<String> recover = IO.<String>raiseError(new RuntimeException()).recover(error -> "hola mundo");
+
+    assertEquals("hola mundo", recover.unsafeRunSync());
+  }
+
+  @Test
+  void recoverWith() {
+    IO<String> recover = IO.<String>raiseError(new IllegalArgumentException())
+        .recover(IllegalArgumentException.class, error -> "hola mundo");
+
+    assertEquals("hola mundo", recover.unsafeRunSync());
+  }
+
+  @Test
+  void recoverWithNotMatch() {
+    IO<String> recover = IO.<String>raiseError(new IllegalArgumentException())
+        .recover(NoSuchElementException.class, error -> "hola mundo");
+
+    assertThrows(IllegalArgumentException.class, recover::unsafeRunSync);
+  }
+
+  @Test
+  void retry(@Mock Supplier<String> computation) {
+    when(computation.get()).thenThrow(UnsupportedOperationException.class);
+
+    Try<String> retry = IO.task(computation).retry().safeRunSync();
+
+    assertTrue(retry.isFailure());
+    verify(computation, times(2)).get();
+  }
+
+  @Test
+  void retryFailure(@Mock Supplier<String> computation) {
+    when(computation.get()).thenThrow(UnsupportedOperationException.class);
+
+    Try<String> retry = IO.task(computation).retry(Duration.ofMillis(100), 3).safeRunSync();
+
+    assertTrue(retry.isFailure());
+    verify(computation, times(4)).get();
+  }
+
+  @Test
+  void retrySuccess(@Mock Supplier<String> computation) {
+    when(computation.get())
+        .thenThrow(UnsupportedOperationException.class)
+        .thenThrow(UnsupportedOperationException.class)
+        .thenThrow(UnsupportedOperationException.class)
+        .thenReturn("hola");
+
+    Try<String> retry = IO.task(computation).retry(Duration.ofMillis(100), 3).safeRunSync();
+
+    assertEquals("hola", retry.get());
+    verify(computation, times(4)).get();
+  }
+
+  @Test
+  void repeatSuccess(@Mock Supplier<String> computation) {
+    when(computation.get()).thenReturn("hola");
+
+    Try<String> repeat = IO.task(computation).repeat(Duration.ofMillis(100), 3).safeRunSync();
+
+    assertEquals("hola", repeat.get());
+    verify(computation, times(4)).get();
+  }
+
+  @Test
+  void repeatFailure(@Mock Supplier<String> computation) {
+    when(computation.get()).thenReturn("hola").thenThrow(UnsupportedOperationException.class);
+
+    Try<String> repeat = IO.task(computation).repeat(Duration.ofMillis(100), 3).safeRunSync();
+
+    assertTrue(repeat.isFailure());
+    verify(computation, times(2)).get();
+  }
+
+  @Test
+  void repeat(@Mock Supplier<String> computation) {
+    when(computation.get()).thenReturn("hola");
+
+    Try<String> repeat = IO.task(computation).repeat().safeRunSync();
+
+    assertEquals("hola", repeat.get());
+    verify(computation, times(2)).get();
+  }
+
+  @Test
+  void flatMapped() {
+    IO<String> io = IO.unit()
+        .map(ignore -> "hola")
+        .map(ignore -> "hola")
+        .map(ignore -> "hola")
+        .map(ignore -> "adios");
+
+    assertEquals("adios", io.unsafeRunSync());
+  }
+
+  @Test
+  void stackSafety() {
+    IO<Integer> sum = sum(100000, 0);
+
+    Future<Integer> futureSum = sum.runAsync();
+
+    assertEquals(705082704, sum.unsafeRunSync());
+    assertEquals(Try.success(705082704), futureSum.await(1, TimeUnit.SECONDS).toTry());
+  }
+
+  @Test
+  void timed() {
+    IO<Tuple2<Duration, Integer>> sum = sum(100000, 0).timed();
+
+    Tuple2<Duration, Integer> result = sum.unsafeRunSync();
+
+    assertEquals(705082704, result._2());
+    assertTrue(result._1().toMillis() > 0);
+  }
+  
+  @Test
+  void timeoutFail() {
+    assertThrows(TimeoutException.class, IO.never().timeout(Duration.ofSeconds(1))::unsafeRunSync);
+  }
+  
+  @Test
+  void timeoutSuccess() {
+    assertEquals(1, IO.pure(1).timeout(Duration.ofSeconds(1)).unsafeRunSync());
+  }
+  
+  @Test
+  void traverse() {
+    IO<String> left = IO.task(() -> "left");
+    IO<String> right = IO.task(() -> "right");
+    
+    IO<Seq<String>> traverse = IO.traverse(List.of(left, right));
+    
+    assertEquals(List.of("left", "right"), traverse.unsafeRunSync());
+  }
+
+  @Test
+  void raceA() {
+    IO<Either<Integer, String>> race = IO.race(
+        IO.delay(Duration.ofMillis(10), () -> 10),
+        IO.delay(Duration.ofMillis(100), () -> "b"));
+    
+    Either<Integer, String> orElseThrow = race.unsafeRunSync();
+    
+    assertEquals(Either.left(10), orElseThrow);
+  }
+
+  @Test
+  void raceB() {
+    IO<Either<Integer, String>> race = IO.race(
+        IO.delay(Duration.ofMillis(100), () -> 10),
+        IO.delay(Duration.ofMillis(10), () -> "b"));
+    
+    Either<Integer, String> orElseThrow = race.unsafeRunSync();
+    
+    assertEquals(Either.right("b"), orElseThrow);
+  }
+  
+  @Test
+  void fork() {
+    IO<String> result = IO.pure("hola")
+      .flatMap(hello -> IO.delay(Duration.ofSeconds(1), () -> hello + " toni").fork())
+      .flatMap(Fiber::join);
+    
+    String orElseThrow = result.runAsync().get();
+
+    assertEquals("hola toni", orElseThrow);
+  }
+  
+  @Test
+  void memoize(@Mock Function1<String, String> toUpperCase) {
+    when(toUpperCase.apply(any()))
+      .thenAnswer(args -> args.getArgument(0, String.class).toUpperCase());
+    
+    IO<Function1<String, IO<String>>> memoized = IO.memoize((String str) -> IO.pure(toUpperCase.apply(str)));
+    
+    IO<String> flatMap = memoized.flatMap(x -> x.apply("hola"));
+    flatMap.unsafeRunSync();
+    flatMap.unsafeRunSync();
+    flatMap.unsafeRunSync();
+    flatMap.unsafeRunSync();
+    
+    verify(toUpperCase).apply("hola");
+  }
+  
+  @Test
+  void fibSyncTest() {
+    assertAll(
+        () -> assertEquals(1, fibSync(1).unsafeRunSync()),
+        () -> assertEquals(1, fibSync(2).unsafeRunSync()),
+        () -> assertEquals(2, fibSync(3).unsafeRunSync()),
+        () -> assertEquals(3, fibSync(4).unsafeRunSync()),
+        () -> assertEquals(5, fibSync(5).unsafeRunSync()),
+        () -> assertEquals(8, fibSync(6).unsafeRunSync()),
+        () -> assertEquals(13, fibSync(7).unsafeRunSync()),
+        () -> assertEquals(21, fibSync(8).unsafeRunSync()),
+        () -> assertEquals(55, fibSync(10).unsafeRunSync()),
+        () -> assertEquals(6765, fibSync(20).unsafeRunSync())
+        );
+  }
+  
+  @Test
+  void fibAsyncTest() {
+    assertAll(
+        () -> assertEquals(1, fibAsync(1).unsafeRunSync()),
+        () -> assertEquals(1, fibAsync(2).unsafeRunSync()),
+        () -> assertEquals(2, fibAsync(3).unsafeRunSync()),
+        () -> assertEquals(3, fibAsync(4).unsafeRunSync()),
+        () -> assertEquals(5, fibAsync(5).unsafeRunSync()),
+        () -> assertEquals(8, fibAsync(6).unsafeRunSync()),
+        () -> assertEquals(13, fibAsync(7).unsafeRunSync()),
+        () -> assertEquals(21, fibAsync(8).unsafeRunSync()),
+        () -> assertEquals(55, fibAsync(10).unsafeRunSync()),
+        () -> assertEquals(6765, fibAsync(20).unsafeRunSync())
+        );
+  }
+
+  private IO<Integer> fibSync(int number) {
+    if (number < 2) {
+      return IO.pure(number);
+    }
+    var number1 = fibSync(number - 1);
+    var number2 = fibSync(number - 2);
+    return number1.flatMap(x -> number2.map(y -> x + y));
+  }
+
+  private IO<Integer> fibAsync(int number) {
+    if (number < 2) {
+      return IO.pure(number);
+    }
+    return IO.parMap2(fibAsync(number - 1), fibAsync(number - 2), Integer::sum);
+  }
+
+  private IO<ResultSet> open(ResultSet resultSet) {
+    return IO.pure(resultSet);
+  }
+
+  private Function1<ResultSet, Try<String>> tryGetString(String column) {
+    return rs -> Try.of(() -> getString(column).apply(rs));
+  }
+
+  private CheckedFunction1<ResultSet, String> getString(String column) {
+    return resultSet -> resultSet.getString(column);
+  }
+
+  private IO<Integer> sum(Integer n, Integer sum) {
+    if (n == 0) {
+      return IO.pure(sum);
+    }
+    return IO.suspend(() -> sum(n - 1, sum + n));
+  }
+
+  private IO<List<String>> currentThreadIO() {
+    Ref<List<String>> ref = Ref.of(List.empty());
+    IO<List<String>> currentThread =
+        ref.updateAndGet(list -> list.append(Thread.currentThread().getName()));
+
+    return currentThread
+        .andThen(currentThread
+            .andThen(currentThread
+                .andThen(currentThread
+                    .andThen(currentThread))));
+  }
+}