public void UnSubscribe(IPushSubscriber pushSubscriber, string topic)
        {
            if (!listenerDic.ContainsKey(topic))
            {
                return;
            }
            var pushSubscribers = listenerDic[topic];

            pushSubscribers.Remove(pushSubscriber);
            taskDic[topic].SetListener(pushSubscribers);
        }
        public void Subscribe(IPushSubscriber pushSubscriber, string topic)
        {
            if (!listenerDic.ContainsKey(topic))
            {
                listenerDic.Add(topic, new List <IPushSubscriber>());
            }
            var pushSubscribers = listenerDic[topic];

            pushSubscribers.Add(pushSubscriber);
            if (taskDic.ContainsKey(topic))
            {
                taskDic[topic].SetListener(pushSubscribers);
            }
            pushSubscriber.Initialize();
        }