code: func ByteToString(a []byte) string {
  	const hexDigit = "0123456789abcdef"
  	if len(a) == 0 {
  		return ""
  	}
  	buf := make([]byte, 0, len(a)*3-1)
  	for i, b := range a {
  		if i > 0 {
  			buf = append(buf, ':')
  		}
  		buf = append(buf, hexDigit[b>>4])
  		buf = append(buf, hexDigit[b&0xF])
  	}
  	return string(buf)
  }
docs: // ByteToString return a human readeable string of the byte