code: func HandleAction(action interface{}, context *Context) (err error) {
  	switch a := action.(type) {
  	case ActionFunc:
  		return a(context)
  	case func(*Context) error:
  		return a(context)
  	case func(*Context): // deprecated function signature
  		a(context)
  		return nil
  	}
  
  	return errInvalidActionType
  }
docs: // HandleAction attempts to figure out which Action signature was used.  If
  // it's an ActionFunc or a func with the legacy signature for Action, the func
  // is run!