code: func readComments(f io.Reader) ([]byte, error) {
  	r := &importReader{b: bufio.NewReader(f)}
  	r.peekByte(true)
  	if r.err == nil && !r.eof {
  		// Didn't reach EOF, so must have found a non-space byte. Remove it.
  		r.buf = r.buf[:len(r.buf)-1]
  	}
  	return r.buf, r.err
  }
docs: // readComments is like ioutil.ReadAll, except that it only reads the leading
  // block of comments in the file.