rabbitmq using threads with pika

I'm trying to get a basic queue system with rabbitmq, but when I try to use threads, it only seems to run 1 thread.

my code:

import pika
import threading

rabbit_url = "amqp://user:pass!@127.0.0.1:5672/%2f"

def start(max_threads):
    for i in xrange(max_threads):
        t = threading.Thread(target=run)
        t.start()
        t.join()

def run():
    connection = pika.BlockingConnection(pika.URLParameters(rabbit_url))
    channel = connection.channel()
    channel.basic_consume(callback,
                          queue='docketq',
                          no_ack=True)

    channel.start_consuming()

def callback(ch, method, properties, body):
    do_work(body)

def do_work(body):
    print body