code: func (r *Router) Shutdown() {
  	r.Lock()
  	defer r.Unlock()
  
  	for areaID, area := range r.areas {
  		for datacenter, info := range area.managers {
  			r.removeManagerFromIndex(datacenter, info.manager)
  			close(info.shutdownCh)
  		}
  
  		delete(r.areas, areaID)
  	}
  
  	r.isShutdown = true
  }
docs: // Shutdown removes all areas from the router, which stops all their respective
  // managers. No new areas can be added after the router is shut down.