code: func NewJSONSourceFromFile(f string) (InputSourceContext, error) {
  	data, err := loadDataFrom(f)
  	if err != nil {
  		return nil, err
  	}
  	return NewJSONSource(data)
  }
docs: // NewJSONSourceFromFile returns an InputSourceContext suitable for
  // retrieving config variables from a file (or url) containing JSON
  // data.