code: func (r *Rar) OpenFile(filename string) error {
  	if r.rr != nil {
  		return fmt.Errorf("rar archive is already open for reading")
  	}
  	var err error
  	r.rc, err = rardecode.OpenReader(filename, r.Password)
  	if err != nil {
  		return err
  	}
  	r.rr = &r.rc.Reader
  	return nil
  }
docs: // OpenFile opens filename for reading. This method supports
  // multi-volume archives, whereas Open does not (but Open
  // supports any stream, not just files).