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 {
		t.Errorf("once failed outside run: %d is not 1", *o)
	}
}

func TestOncePanic(t *testing.T) {
	var once Once
	func() {
		defer func() {
			if r := recover(); r == nil {
				t.Fatalf("Once.Do did not panic")
			}
		}()
		once.Do(func() {
			panic("failed")
		})
	}()