code: func (s *StorageOverseer) ResetExpiry(w http.ResponseWriter, r *http.Request) error {
  	sessID, err := s.options.getCookieValue(w, r)
  	if err != nil {
  		return errors.Wrap(err, "unable to get session id from cookie")
  	}
  
  	// Reset the expiry of the server-side session
  	err = s.Storer.ResetExpiry(sessID)
  	if err != nil {
  		return errors.Wrap(err, "unable to reset expiry of server side session")
  	}
  
  	// Reset the expiry in the client-side cookie
  	if s.options.MaxAge != 0 {
  		w.(cookieWriter).SetCookie(s.options.makeCookie(sessID))
  	}
  
  	return nil
  }
docs: // ResetExpiry resets the age of the session to time.Now(), so that
  // MaxAge calculations are renewed