code: func fieldsASCII(s string) []string {
  	fn := func(r rune) bool {
  		switch r {
  		case '\t', '\n', '\f', '\r', ' ':
  			return true
  		}
  		return false
  	}
  	return strings.FieldsFunc(s, fn)
  }
docs: // fieldsASCII is similar to strings.Fields but only allows ASCII whitespaces