public void add(final Channel channel, final List<MqttTopicSubscription> mqttTopicSubscription) {
        CompletableFuture.runAsync(() -> mqttTopicSubscription.parallelStream().forEach(s -> {
            List<Channel> channels = get(s.topicName());
            channels.add(channel);
            TOPIC_CHANNEL_FACTORY.put(s.topicName(), channels);
        }));
    }
add subscribe channel.
@param channel channel
@param mqttTopicSubscription mqtt subscription info
shenyu-protocol/shenyu-protocol-mqtt/src/main/java/org/apache/shenyu/protocol/mqtt/repositories/SubscribeRepository.java