code: func newBzip2Writer(w io.Writer) (wc io.WriteCloser, err error) {
  	var bw bzip2Writer
  	bw.c = exec.Command("bzip2", "-c")
  	bw.c.Stdout = w
  
  	if bw.w, err = bw.c.StdinPipe(); err != nil {
  		return nil, err
  	}
  
  	if err = bw.c.Start(); err != nil {
  		return nil, err
  	}
  
  	return bw, nil
  }
docs: // Package compress/bzip2 implements only decompression,
  // so we'll fake it by running bzip2 in another process.