code: func openFile(name string) (*tar.Reader, *os.File, error) {
  	f, err := os.Open(name)
  	if err != nil {
  		return nil, nil, err
  	}
  
  	gr, err := gzip.NewReader(f)
  	if err != nil {
  		f.Close()
  		return nil, nil, err
  	}
  
  	return tar.NewReader(gr), f, nil
  }
docs: // openFile opens a tar.gz file with gzip and tar decoders.