code: func (p *Parser) lookahead(context ParserContext) (Token, string) {
  	tok, lit := p.scannedItems[p.position].tok, p.scannedItems[p.position].literal
  	if context == Values {
  		switch tok {
  		case InToken, NotInToken:
  			tok = IdentifierToken
  		}
  	}
  	return tok, lit
  }
docs: // lookahead func returns the current token and string. No increment of current position