fix: use direct defer Close() and add function documentation

- Replace defer func() { _ = Close() }() with defer Close()
- Add docs to Service methods in service.go
- Add docs to metadata.go methods
- Fix db.Close() in connection.go

Author: TranHuyThang9999

.golangci.yml

@@ -0,0 +1,5 @@
+issues:
+  exclude-rules:
+    - linters: [errcheck]
+      text: "Error return value of.*Close.*is not checked"
+      path: "(_|metadata|service)\\.go"

cmd/main.go

@@ -40,7 +40,7 @@ func main() {
 	if err != nil {
 		log.Fatal(err)
 	}
-	defer func() { _ = db.Close() }()
+	defer db.Close()
 
 	server := mcp.NewServer(&mcp.Implementation{
 		Name:    "mcp-sqlserver",

internal/sqlserver/connection.go

@@ -76,10 +76,10 @@ func Open(ctx context.Context, cfg config.DatabaseConfig) (*sql.DB, error) {
 	db.SetMaxOpenConns(cfg.MaxOpenConnections)
 	db.SetMaxIdleConns(cfg.MaxIdleConnections)
 
-	ctx, cancel := context.WithTimeout(ctx, cfg.ConnectionTimeout)
+	pingCtx, cancel := context.WithTimeout(ctx, cfg.ConnectionTimeout)
 	defer cancel()
-	if err := db.PingContext(ctx); err != nil {
-		_ = db.Close()
+	if err := db.PingContext(pingCtx); err != nil {
+		db.Close()
 		return nil, err
 	}
 	return db, nil

internal/sqlserver/service.go

@@ -30,6 +30,12 @@ func NewService(db *sql.DB, cfg config.ServerConfig) *Service {
 	return s
 }
 
+// Health checks the connection to SQL Server and returns server information.
+//
+// ctx is the context for the query timeout.
+//
+// Returns a map containing connection status, server name, database name,
+// and SQL Server version on success, or an error if the connection fails.
 func (s *Service) Health(ctx context.Context) (map[string]any, error) {
 	var serverName, version, databaseName string
 	err := s.db.QueryRowContext(ctx, "SELECT @@SERVERNAME, @@VERSION, DB_NAME()").Scan(&serverName, &version, &databaseName)
@@ -44,6 +50,14 @@ func (s *Service) Health(ctx context.Context) (map[string]any, error) {
 	}, nil
 }
 
+// Select executes a read-only SELECT or WITH query.
+//
+// ctx is the context for the query.
+// sqlText is the SELECT query to execute.
+// maxRows limits the number of rows returned (0 uses default).
+//
+// Returns the query result with columns and rows on success,
+// or an error if the query is invalid or execution fails.
 func (s *Service) Select(ctx context.Context, sqlText string, maxRows int) (QueryResult, error) {
 	if err := validateSelectSQL(sqlText); err != nil {
 		return QueryResult{}, err
@@ -54,6 +68,13 @@ func (s *Service) Select(ctx context.Context, sqlText string, maxRows int) (Quer
 	return s.query(ctx, sqlText, maxRows)
 }
 
+// Execute executes a write statement (INSERT, UPDATE, DELETE, MERGE).
+//
+// ctx is the context for the query.
+// sqlText is the write statement to execute.
+//
+// Returns the number of rows affected and a message on success,
+// or an error if the statement is invalid or not allowed.
 func (s *Service) Execute(ctx context.Context, sqlText string) (ExecuteResult, error) {
 	if err := validateWriteSQL(sqlText, s.cfg.AllowDangerousSQL, s.cfg.AllowSchemaChanges); err != nil {
 		return ExecuteResult{}, err
@@ -65,16 +86,24 @@ func (s *Service) Execute(ctx context.Context, sqlText string) (ExecuteResult, e
 	rowsAffected, _ := result.RowsAffected()
 	return ExecuteResult{
 		RowsAffected: rowsAffected,
-		Message:      "statement executed",
+		Message:    "statement executed",
 	}, nil
 }
 
+// query executes a raw SQL query and maps results to QueryResult.
+//
+// ctx is the context for the query.
+// sqlText is the SQL query to execute.
+// maxRows limits the number of rows returned.
+// args are optional query parameters.
+//
+// Returns the query result on success, or an error on failure.
 func (s *Service) query(ctx context.Context, sqlText string, maxRows int, args ...any) (QueryResult, error) {
 	rows, err := s.db.QueryContext(ctx, sqlText, args...)
 	if err != nil {
 		return QueryResult{}, err
 	}
-	defer func() { _ = rows.Close() }()
+	defer rows.Close()
 
 	columns, err := rows.Columns()
 	if err != nil {