golangci-lint: add sqlclosecheck linter and fixes (#18844)

Signed-off-by: Tim Vaillancourt <[email protected]>

Author: timvaillancourt

.golangci.yml

@@ -11,6 +11,7 @@ linters:
     - govet
     - ineffassign
     - perfsprint
+    - sqlclosecheck
     - staticcheck
     - whitespace
   settings:
@@ -155,6 +156,7 @@ linters:
         path: ^go/stats/statsd/
       - linters:
           - errcheck
+          - sqlclosecheck
         path: ^go/test/
       - linters:
           - errcheck

go/vt/vitessdriver/driver_test.go

@@ -569,6 +569,7 @@ func TestTx(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer s.Close()
 
 	_, err = s.Exec(int64(0))
 	if err != nil {
@@ -594,10 +595,12 @@ func TestTx(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	_, err = s.Query(int64(0))
+	defer s.Close()
+	r, err := s.Query(int64(0))
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer r.Close()
 	err = tx.Rollback()
 	if err != nil {
 		t.Fatal(err)
@@ -648,6 +651,7 @@ func TestSessionToken(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer s.Close()
 
 	_, err = s.Exec(int64(0))
 	if err != nil {
@@ -674,6 +678,7 @@ func TestSessionToken(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer newS.Close()
 
 	_, err = newS.Exec(int64(1))
 	if err != nil {

go/vt/vtadmin/cluster/cluster.go

@@ -1318,6 +1318,7 @@ func (c *Cluster) getTablets(ctx context.Context) ([]*vtadminpb.Tablet, error) {
 	if err != nil {
 		return nil, err
 	}
+	defer rows.Close()
 
 	return c.parseTablets(rows)
 }

go/vt/vtadmin/vtsql/vtsql.go

@@ -178,7 +178,8 @@ func (vtgate *VTGateProxy) ShowTablets(ctx context.Context) (*sql.Rows, error) {
 
 	vtadminproto.AnnotateClusterSpan(vtgate.cluster, span)
 
-	return vtgate.conn.QueryContext(vtgate.getQueryContext(ctx), "SHOW vitess_tablets")
+	// The caller must run .Close() if the *sql.Rows != nil. We will suppress the sqlclosecheck linter here.
+	return vtgate.conn.QueryContext(vtgate.getQueryContext(ctx), "SHOW vitess_tablets") //nolint:sqlclosecheck
 }
 
 // VExplain is part of the DB interface.
@@ -189,10 +190,11 @@ func (vtgate *VTGateProxy) VExplain(ctx context.Context, query string, vexplainS
 	vtadminproto.AnnotateClusterSpan(vtgate.cluster, span)
 
 	rows, err := vtgate.conn.QueryContext(vtgate.getQueryContext(ctx), query)
-
 	if err != nil {
 		return nil, err
 	}
+	defer rows.Close()
+
 	switch vexplainStmt.Type {
 	case sqlparser.QueriesVExplainType:
 		return convertVExplainQueriesResultToString(rows)