fix waitAll (#23)

wait_all.go

@@ -19,6 +19,13 @@ type WaitAllOptions struct {
 // first error from any tasks passed in will be returned.
 func WaitAll(ctx context.Context, options *WaitAllOptions, tasks ...Waitable) error {
 	tasksCount := len(tasks)
+	if tasksCount == 0 {
+		return nil
+	}
+
+	if options == nil {
+		options = &WaitAllOptions{}
+	}
 
 	errorCh := make(chan error, tasksCount)
 	// when failFast enabled, we return on first error we see, while other task may still post error in this channel.

wait_all_test.go

@@ -126,3 +126,12 @@ func TestWaitAllCanceled(t *testing.T) {
 	// wait minor time for the go routine to finish.
 	time.Sleep(1 * time.Millisecond)
 }
+
+func TestWaitAllWithNoTasks(t *testing.T) {
+	t.Parallel()
+	ctx, cancelFunc := newTestContextWithTimeout(t, 1*time.Millisecond)
+	defer cancelFunc()
+
+	err := asynctask.WaitAll(ctx, nil)
+	assert.NoError(t, err)
+}