求助：关于 Channels2.0 的使用问题

问题背景：

我需要在后台订阅 redis 的消息，一有消息就给前端推信息。所以我这么做了：

    async def connect(self):
        logger.info("websocket connected.")
        redis_conn = StrictRedis(**settings.REDIS_DB)
        self.ps = redis_conn.pubsub()
        await self.ps.subscribe(settings.REDIS_CHANNELS)

        await self.accept()

    async def disconnect(self, code):
        logger.info("websocket disconnected.")
        await self.ps.unsubscribe()
        await self.close()

    async def receive(self, text_data=None, bytes_data=None):
        logger.info("websocket received data.\n%s" % text_data)
        try:
            data = json.loads(text_data)
            self.user_id = data['payload'].get('user_id')
        except json.JSONDecodeError:
            await self.close()

        while True:
            # 获取 redis 的消息
            msg = await self.get_msg_from_queue()
            if not msg:
                continue
            logger.info("get msg %s" % msg)
            await self.send(text_data=json.dumps(msg))

打开前端页面的时候，链接成功 websocket 会立马发一个信息，来对接，后端确认以后开始等 redis 的消息，这里我使用的 while 循环，就是因为这个 while 循环，导致我前端断开 websocket 链接以后，后端不会触发 disconnect()函数，所有就没有关闭这个实例，导致后端不断报这个错误：

WARNING  Application instance <Task pending coro=<AsyncConsumer.__call__() 
running at /xxx/venv/lib/python3.6/site-packages/channels/consumer.py:54> 
wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x7fade64e0678>()]>> 
for connection <WebSocketProtocol client=['127.0.0.1', 49204] path=b'/listen'> 
took too long to shut down and was killed.

求助 V 站大佬，我该如何在 while 循环中来判断当前客户端是否断开呢？