任务执行过程
如果调用线程与EventLoop所在的线程是同一线程，任务直接执行，否则会放入EventLoop的队列中，下次执行。
“Never put a long-running task in the execution queue, because it will block any other task from executing on the same thread.” If you must make blocking calls or execute long-running tasks, we advise the use of a dedicated EventExecutor
