code: func OptSrcPath(pathname string) SrcOption {
  	return func(s *Source) error {
  		info, err := os.Stat(pathname)
  		if err != nil {
  			return errors.Wrap(err, "statting path")
  		}
  		if info.IsDir() {
  			infos, err := ioutil.ReadDir(pathname)
  			if err != nil {
  				return errors.Wrap(err, "reading directory")
  			}
  			s.files = make([]string, 0, len(infos))
  			for _, info = range infos {
  				s.files = append(s.files, path.Join(pathname, info.Name()))
  			}
  		} else {
  			s.files = []string{pathname}
  		}
  		return nil
  	}
  }
docs: // OptSrcPath sets the path name for the file or directory to use for source
  // data.