code: func (s *Server) AddListener(listener func(config.Configuration)) {
  	if s.configurationListeners == nil {
  		s.configurationListeners = make([]func(config.Configuration), 0)
  	}
  	s.configurationListeners = append(s.configurationListeners, listener)
  }
docs: // AddListener adds a new listener function used when new configuration is provided