code: func encodeBase64(s string) string {
  	const lineLen = 70
  	encLen := base64.StdEncoding.EncodedLen(len(s))
  	lines := encLen/lineLen + 1
  	buf := make([]byte, encLen*2+lines)
  	in := buf[0:encLen]
  	out := buf[encLen:]
  	base64.StdEncoding.Encode(in, []byte(s))
  	k := 0
  	for i := 0; i < len(in); i += lineLen {
  		j := i + lineLen
  		if j > len(in) {
  			j = len(in)
  		}
  		k += copy(out[k:], in[i:j])
  		if lines > 1 {
  			out[k] = '\n'
  			k++
  		}
  	}
  	return string(out[:k])
  }
docs: // encodeBase64 encodes s as base64 that is broken up into multiple lines
  // as appropriate for the resulting length.