private function connect()
 {
     self::$connection = new AMQPStreamConnection(self::RABBIT_MQ_HOST, self::RABBIT_MQ_PORT, self::RABBIT_MQ_USER, self::RABBIT_MQ_PASSWORD);
     self::$channel = self::$connection->channel();
     self::$channel->queue_declare(self::RABBIT_MQ_QUEUE, false, true, false, false);
 }