code: func (u *UlimitsConfig) MarshalJSON() ([]byte, error) {
  	if u.Single != 0 {
  		return json.Marshal(u.Single)
  	}
  	// Pass as a value to avoid re-entering this method and use the default implementation
  	return json.Marshal(*u)
  }
docs: // MarshalJSON makes UlimitsConfig implement json.Marshaller