code: func (c HubConfig) GetString(key string, defval string) string {
  	val, ok := c[key]
  	if ok {
  		s, ok := val.(string)
  		if ok && len(s) > 0 {
  			return s
  		}
  		// TODO only primitive types
  		return fmt.Sprintf("%s", val)
  	}
  	return defval
  }
docs: // GetString property.