code: func find(data []byte, start int, target rune) (index int) {
  	index = bytes.IndexRune(data[start:], target)
  	if index != -1 {
  		return index + start
  	}
  	return index
  }
docs: // find returns the index of first target in data starting from `start`.
  // It returns -1 if target not found.