code: func (ed *Dispatcher) HandleRegisterConnectionEvent(e esdispatcher.Event) {
  	evt := e.(*RegisterConnectionEvent)
  
  	if ed.connectionRegistration != nil {
  		evt.ErrCh <- errors.New("registration already exists for connection event")
  		return
  	}
  
  	ed.connectionRegistration = evt.Reg
  	evt.RegCh <- evt.Reg
  }
docs: // HandleRegisterConnectionEvent registers a connection listener