From a77de922988631477a199aca1ed7c4732e649782 Mon Sep 17 00:00:00 2001
From: Eugene R <reugpro@gmail.com>
Date: Fri, 28 Jul 2023 13:38:04 +0300
Subject: [PATCH] fix goroutine leak after calling Future.Get() (#8)

---
 future.go      |  4 ++--
 future_test.go | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/future.go b/future.go
index 87c9440..7cfe66d 100644
--- a/future.go
+++ b/future.go
@@ -50,7 +50,7 @@ var _ Future[any] = (*FutureImpl[any])(nil)
 // NewFuture returns a new Future.
 func NewFuture[T any]() Future[T] {
 	return &FutureImpl[T]{
-		done: make(chan interface{}),
+		done: make(chan interface{}, 1),
 	}
 }
 
@@ -71,7 +71,7 @@ func (fut *FutureImpl[T]) acceptTimeout(timeout time.Duration) {
 		case result := <-fut.done:
 			fut.setResult(result)
 		case <-timer.C:
-			fut.err = fmt.Errorf("Future timeout after %s", timeout)
+			fut.setResult(fmt.Errorf("Future timeout after %s", timeout))
 		}
 	})
 }
diff --git a/future_test.go b/future_test.go
index 591bf8a..5bf3d9f 100644
--- a/future_test.go
+++ b/future_test.go
@@ -2,6 +2,9 @@ package async
 
 import (
 	"errors"
+	"fmt"
+	"runtime"
+	"sync"
 	"testing"
 	"time"
 
@@ -106,3 +109,36 @@ func TestFutureTimeout(t *testing.T) {
 	_, err = future.Join()
 	internal.AssertErrorContains(t, err, "timeout")
 }
+
+func TestFutureGoroutineLeak(t *testing.T) {
+	var wg sync.WaitGroup
+
+	fmt.Println(runtime.NumGoroutine())
+
+	numFuture := 100
+	for i := 0; i < numFuture; i++ {
+		promise := NewPromise[string]()
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			time.Sleep(time.Millisecond * 100)
+			promise.Success("OK")
+		}()
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			fut := promise.Future()
+			_, _ = fut.Get(time.Millisecond * 10)
+			time.Sleep(time.Millisecond * 100)
+			_, _ = fut.Join()
+		}()
+	}
+
+	wg.Wait()
+	time.Sleep(time.Millisecond * 10)
+	numGoroutine := runtime.NumGoroutine()
+	fmt.Println(numGoroutine)
+	if numGoroutine > numFuture {
+		t.Fatalf("numGoroutine is %d", numGoroutine)
+	}
+}