我在下面為異步池編寫了代碼。在__aexit__任務完成后我取消了 _worker 任務。但是當我運行代碼時，工作任務不會被取消并且代碼會永遠運行。這就是任務的樣子：<Task pending coro=<AsyncPool._worker() running at \async_pool.py:17> wait_for=<Future cancelled>>。正在asyncio.wait_for取消但不是工作任務。class AsyncPool:    def __init__(self,coroutine,no_of_workers,timeout):        self._loop           = asyncio.get_event_loop()        self._queue          = asyncio.Queue()        self._no_of_workers  = no_of_workers        self._coroutine      = coroutine        self._timeout        = timeout        self._workers        = None    async def _worker(self):         while True:            try:                ret = False                queue_item           = await self._queue.get()                ret = True                result               = await asyncio.wait_for(self._coroutine(queue_item), timeout = self._timeout,loop= self._loop)            except Exception as e:                print(e)            finally:                if ret:                    self._queue.task_done()    async def push_to_queue(self,item):        self._queue.put_nowait(item)        async def __aenter__(self):        assert self._workers == None        self._workers = [asyncio.create_task(self._worker()) for _ in range(self._no_of_workers)]        return self        async def __aexit__(self,type,value,traceback):        await self._queue.join()        for worker in self._workers:            worker.cancel()        await asyncio.gather(*self._workers, loop=self._loop, return_exceptions =True)要使用異步池：async def something(item):    print("got", item)    await asyncio.sleep(item) async def main():    async with AsyncPool(something, 5, 2) as pool:        for i in range(10):            await pool.push_to_queue(i) asyncio.run(main())我終端的輸出：