*o++
}

func run(t *testing.T, once *Once, o *one, c chan bool) {
	once.Do(func() { o.Increment() })
	if v := *o; v != 1 {
		t.Errorf("once failed inside run: %d is not 1", v)
	}
	c <- true
}

func TestOnce(t *testing.T) {
	o := new(one)
	once := new(Once)
	c := make(chan bool)
	const N = 10
	for i := 0; i < N; i++ {
		go run(t, once, o, c)
	}
	for i := 0; i < N; i++ {
		<-c
	}
	if *o != 1 {