code: func NewNotifyingCommentsController(service *goa.Service, db application.DB, notificationChannel notification.Channel, config CommentsControllerConfiguration) *CommentsController {
  	n := notificationChannel
  	if n == nil {
  		n = &notification.DevNullChannel{}
  	}
  	return &CommentsController{
  		Controller:   service.NewController("CommentsController"),
  		db:           db,
  		notification: n,
  		config:       config,
  	}
  }
docs: // NewNotifyingCommentsController creates a comments controller with notification broadcast.