我无法从Pika返回数据，因为它start_consuming没有停止。它打印结果，但不返回输出

def on_request(ch, method, props, body):
    directory =body

    print(directory.decode('utf-8'))
    response = parse(directory.decode('utf-8'))

    ch.basic_publish(exchange='',
                     routing_key=props.reply_to,
                     properties=pika.BasicProperties(correlation_id = \
                                                         props.correlation_id),
                     body=str(response))
    ch.basic_ack(delivery_tag=method.delivery_tag)
def start():
    print("hi")
    connection = pika.BlockingConnection(
        pika.ConnectionParameters(host='localhost'))

    channel = connection.channel()

    channel.queue_declare(queue='rpc_queue')

    channel.basic_qos(prefetch_count=2)
    channel.basic_consume(queue='rpc_queue', on_message_callback=on_request)

    print(" [x] Awaiting RPC requests")
    channel.start_consuming()