code: func lastToken(data []byte) int {
  	for i := len(data) - 1; i >= 0; i-- {
  		switch data[i] {
  		case ' ', '\n', '\r', '\t':
  			continue
  		default:
  			return i
  		}
  	}
  
  	return -1
  }
docs: // Find position of last character which is not whitespace