defer wg.Done()
		if failed {
			return nil
		}
		failed = true
		return errors.New("fake error")
	})

	go q.Run(stop)

	// wait for the task to run twice.
	wg.Wait()
}

func TestResourceFree(t *testing.T) {
	q := NewQueue(1 * time.Microsecond)
	stop := make(chan struct{})
	signal := make(chan struct{})
	go func() {
		q.Run(stop)
		signal <- struct{}{}
	}()

	q.Push(func() error {