subscribe的时候，没有既定topic，就直接报TOPIC_NOT_FOUND

[cjzyy]

按照nsq的文档，subscribe的时候如果没有对应topic，则会直接生成subscribe设置的topic，希望改进

[androzd]

For topic not found you can use:

Not sure

try {
    $nsq->subscribe(
        $topic,
        $channel,
        function (NsqMessage $nsqMessage, $bev) use ($topic, $channel) {
           ...
        }
    );
} catch (NsqException $nsqException) {
    if ($nsqException->getCode() == NSQ_ERROR_TOPIC_NOT_EXISTS) {
        logger()->debug('Waiting for topic creation');
        sleep(5);
    }
}