code: func (p *Parser) ParseUInt64() (uint64, error) {
  	tok, pos, lit := p.ScanIgnoreWhitespace()
  	if tok != INTEGER {
  		return 0, newParseError(tokstr(tok, lit), []string{"integer"}, pos)
  	}
  
  	// Convert string to unsigned 64-bit integer
  	n, err := strconv.ParseUint(lit, 10, 64)
  	if err != nil {
  		return 0, &ParseError{Message: err.Error(), Pos: pos}
  	}
  
  	return uint64(n), nil
  }
docs: // ParseUInt64 parses a string and returns a 64-bit unsigned integer literal.