code: func (s Session) Set(key string, value interface{}) error {
  	if value == nil {
  		s.Del(key)
  		return nil
  	}
  
  	s[key] = value
  	return nil
  }
docs: // Places the object into the session, a nil value will cause remove the key from the session
  // (or you can use the Session.Del(key) function