code: func (c Config) ReadFrom(r io.Reader) (int64, error) {
  	data, err := ioutil.ReadAll(r)
  	if err != nil {
  		return int64(len(data)), err
  	}
  	if err = json.Unmarshal(data, &c); err != nil {
  		return int64(len(data)), err
  	}
  	return int64(len(data)), nil
  }
docs: // ReadFrom implements the io.ReaderFrom interface. This
  // should be used with io.Reader to load configuration from
  //file or from string etc.