@Override
    public List<Channel> get(final List<String> topics) {
        Set<Channel> channels = new CopyOnWriteArraySet<>();
        topics.parallelStream().forEach(s -> channels.addAll(TOPIC_CHANNEL_FACTORY.get(s)));
        return new CopyOnWriteArrayList<>(channels);
    }
remove subscribe channel.
@param topics topics
@param channel channel
shenyu-protocol/shenyu-protocol-mqtt/src/main/java/org/apache/shenyu/protocol/mqtt/repositories/SubscribeRepository.java