Revert "Revert "audio: No need goroutine for tests""

This reverts commit 62a9bb195c.

audio/audio_test.go

@@ -71,9 +71,6 @@ func TestGC(t *testing.T) {
 	p = nil
 	runtime.GC()
 
-	ch := make(chan struct{})
-	go func() {
-		defer close(ch)
 	for i := 0; i < 10; i++ {
 		got = PlayersNumForTesting()
 		if want := 0; got == want {
@@ -84,7 +81,4 @@ func TestGC(t *testing.T) {
 		time.Sleep(100 * time.Millisecond)
 	}
 	t.Errorf("time out")
-	}()
-
-	<-ch
 }