drain tasks in an unblocked way to avoid data race

pond.go

@@ -370,13 +370,14 @@ func (p *WorkerPool) stop(waitForQueuedTasksToComplete bool) {
 	// Terminate all workers & purger goroutine
 	p.contextCancel()
 
+	// Wait for all workers & purger goroutine to exit
+	p.workersWaitGroup.Wait()
+
 	// close tasks channel (only once, in case multiple concurrent calls to StopAndWait are made)
 	p.tasksCloseOnce.Do(func() {
 		close(p.tasks)
 	})
 
-	// Wait for all workers & purger goroutine to exit
-	p.workersWaitGroup.Wait()
 }
 
 // purge represents the work done by the purger goroutine

pond_blackbox_test.go

@@ -406,6 +406,28 @@ func TestPoolWithCustomIdleTimeout(t *testing.T) {
 	pool.StopAndWait()
 }
 
+func TestStopWithPurging(t *testing.T) {
+
+	pool := pond.New(5, 5, pond.IdleTimeout(100*time.Millisecond))
+
+	// Submit a task
+	for i := 0; i < 5; i++ {
+		pool.Submit(func() {
+			time.Sleep(10 * time.Millisecond)
+		})
+	}
+
+	assertEqual(t, 5, pool.RunningWorkers())
+
+	// Purge goroutine is clearing idle workers
+	time.Sleep(200 * time.Millisecond)
+
+	// Stop the pool to make sure there is no data race with purge goroutine
+	pool.StopAndWait()
+
+	assertEqual(t, 0, pool.RunningWorkers())
+}
+
 func TestPoolWithCustomPanicHandler(t *testing.T) {
 
 	var capturedPanic interface{} = nil

worker.go

@@ -46,7 +46,14 @@ func worker(context context.Context, waitGroup *sync.WaitGroup, firstTask func()
 
 // drainPendingTasks discards queued tasks and decrements the corresponding wait group
 func drainTasks(tasks <-chan func(), tasksWaitGroup *sync.WaitGroup) {
-	for _ = range tasks {
-		tasksWaitGroup.Done()
+	for {
+		select {
+		case task, ok := <-tasks:
+			if task != nil && ok {
+				tasksWaitGroup.Done()
+			}
+		default:
+			return
+		}
 	}
 }