code: func isDelimiter(ch rune, delimiters ...rune) bool {
  	if delimiters == nil {
  		return unicode.IsSpace(ch)
  	}
  	for _, delimiter := range delimiters {
  		if ch == delimiter {
  			return true
  		}
  	}
  	return false
  }
docs: // private function (lower case func name)