/// <summary>
/// 订阅消息
/// </summary>
/// <param name="topic">消息主题</param>
/// <param name="group">消息分组</param>
/// <param name="handler">消息处理器</param>
public void Subscribe(string topic, string group, Func <ReadOnlyMemory <byte>, ulong, Task> handler)
{
var channel = channels.GetOrAdd(group, _rabbitMQClient.GetChannel());
channel.Subscribe(topic, group, handler);
}