Why I can not only close channel?

[huanhuang]

I want close channel when I published a message, I call channel.close() ,but channel didn't closed even if I call the channel.is_closed() returned True. Through the RabbitMQ Manager, I still see the channel. if I publish multi message, it will reached max channel number, then raise exception. but I don't know how to close channel if I had published a msg.Following is example code:

routing_key = "test_queue"
msg_id = 0
while True:
    channel: aio_pika.abc.AbstractChannel = await connection.channel()
    await channel.declare_queue(routing_key, durable=True)
    print(channel.number)
    exchange = channel.default_exchange
    await exchange.publish(
        aio_pika.Message(
            body='Hello {}'.format(msg_id).encode(), delivery_mode=aio_pika.DeliveryMode.PERSISTENT
        ),
        routing_key=routing_key,
        timeout=10
    )
    await channel.close()
    await asyncio.sleep(0.1)
    msg_id += 1