code: func indexRuneWithEscaping(s string, r rune) int {
  	end := strings.IndexRune(s, r)
  	if end == -1 {
  		return -1
  	}
  	if end > 0 && s[end-1] == '\\' {
  		start := end + utf8.RuneLen(r)
  		end = indexRuneWithEscaping(s[start:], r)
  		if end != -1 {
  			end += start
  		}
  	}
  	return end
  }
docs: // Find the first index of a rune in a string,
  // ignoring any times the rune is escaped using "\".