mu.Lock()
		for !written {
			mu.Unlock()
			time.Sleep(100 * time.Microsecond)
			mu.Lock()
		}
		mu.Unlock()
		x = 1
		ch <- true
	}()
	<-ch
	<-ch
}

func TestNoRaceMutexSemaphore(t *testing.T) {
	var mu sync.Mutex
	ch := make(chan bool, 2)
	x := 0
	_ = x
	mu.Lock()
	go func() {
		x = 1
		mu.Unlock()
		ch <- true
	}()
	go func() {
		mu.Lock()