code: func NewJSONSourceFromReader(r io.Reader) (InputSourceContext, error) {
  	data, err := ioutil.ReadAll(r)
  	if err != nil {
  		return nil, err
  	}
  	return NewJSONSource(data)
  }
docs: // NewJSONSourceFromReader returns an InputSourceContext suitable for
  // retrieving config variables from an io.Reader that returns JSON data.