impl TaskId {
    /// Generates a new `TaskId`.
    pub(crate) fn generate() -> TaskId {
        // TODO: find a good version to emulate u64 atomics on 32 bit systems.
        static COUNTER: AtomicUsize = AtomicUsize::new(1);

        let id = COUNTER.fetch_add(1, Ordering::Relaxed);
        if id > usize::max_value() / 2 {
            std::process::abort();
        }
        TaskId(id)
    }
}

服务器程序运行足够久后，会因为 std::process::abort() 而退出。