code: func (v *FileVisitor) Visit(fn VisitorFunc) error {
  	var f *os.File
  	if v.Path == constSTDINstr {
  		f = os.Stdin
  	} else {
  		var err error
  		if f, err = os.Open(v.Path); err != nil {
  			return err
  		}
  	}
  	defer f.Close()
  	v.StreamVisitor.Reader = f
  
  	return v.StreamVisitor.Visit(fn)
  }
docs: // Visit in a FileVisitor is just taking care of opening/closing files