code: func expectKeyWord(parser *Parser, value string) (lexer.Token, error) {
  	token := parser.Token
  	if token.Kind == lexer.NAME && token.Value == value {
  		return token, advance(parser)
  	}
  	descp := fmt.Sprintf("Expected \"%s\", found %s", value, lexer.GetTokenDesc(token))
  	return token, gqlerrors.NewSyntaxError(parser.Source, token.Start, descp)
  }
docs: // If the next token is a keyword with the given value, return that token after
  // advancing the parser. Otherwise, do not change the parser state and return false.