if now != g {
			t.Fatalf("%d goroutines created", now-g)
		}
	}
	checkCreatedGoroutine := func() {
		t.Helper()
		now := goroutines.Load()
		if now != g+1 {
			t.Fatalf("%d goroutines created, want 1", now-g)
		}
		g = now
	}

	_, cancel0 := WithCancel(&myDoneCtx{Background()})
	cancel0()
	checkCreatedGoroutine()

	_, cancel0 = WithTimeout(&myDoneCtx{Background()}, veryLongDuration)