code: func sanitizeKeyMod(s string) string {
  	n := ""
  	for _, v := range s {
  		if 'a' <= v && v <= 'z' {
  			v = unicode.ToUpper(v)
  		} else if ('Z' < v || v < 'A') && ('9' < v || v < '0') {
  			v = '_'
  		}
  		// If (n == "" && v == '_'), then we will skip as this is the beginning with '_'
  		if !(n == "" && v == '_') {
  			n += string(v)
  		}
  	}
  	return n
  }
docs: // sanitizeKeyMode returns the sanitized string so that it could be used in journald.
  // In journald log, there are special requirements for fields.
  // Fields must be composed of uppercase letters, numbers, and underscores, but must
  // not start with an underscore.