fix: notify group Done listeners on context cancellation

group_done_cancel_test.go

@@ -0,0 +1,32 @@
+package pond
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestTaskGroupDoneClosesOnContextCancellation(t *testing.T) {
+	pool := NewPool(1)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	release := make(chan struct{})
+	t.Cleanup(func() {
+		close(release)
+		pool.StopAndWait()
+	})
+	group := pool.NewGroupContext(ctx)
+	started := make(chan struct{})
+	group.Submit(func() {
+		close(started)
+		<-release
+	})
+	<-started
+	done := group.Done()
+	cancel()
+	select {
+	case <-done:
+	case <-time.After(time.Second):
+		t.Fatal("Done did not close when the group context was cancelled")
+	}
+}

internal/future/composite.go

@@ -67,6 +67,16 @@ func (f *CompositeFuture[V]) Done(count int) <-chan struct{} {
 		ch:    ch,
 	})
 
+	go func() {
+		select {
+		case <-f.ctx.Done():
+			f.mutex.Lock()
+			defer f.mutex.Unlock()
+			f.notifyListeners()
+		case <-ch:
+		}
+	}()
+
 	return ch
 }