code: func QueryTopic(s string) registry.Option {
  	return func(o *registry.Options) {
  		if o.Context == nil {
  			o.Context = context.Background()
  		}
  		o.Context = context.WithValue(o.Context, queryTopicKey{}, s)
  	}
  }
docs: // QueryTopic allows to set a custom nats topic on which service registries
  // query (survey) other services. All registries listen on this topic and
  // then respond to the query message.