code: func (r *Registry) GetServerFunc(stream string) (func(*Peer, string, bool) (Server, error), error) {
  	r.serverMu.RLock()
  	defer r.serverMu.RUnlock()
  
  	f := r.serverFuncs[stream]
  	if f == nil {
  		return nil, fmt.Errorf("stream %v not registered", stream)
  	}
  	return f, nil
  }
docs: // GetServer accessor for incoming streamer constructors