Function wait_unless_stopped 

async fn wait_unless_stopped<T>(
    future: impl Future<Output = T>,
    limit: Duration,
    stop: &CancellationToken,
    stopped: Duration,
) -> Option<T>

Wait for future for at most limit, and only for stopped more once the shutdown stopped the call through stop, see ChildReaper::STOP_BUDGET. None if it did not finish by then.