address comments

loader/checkpoint.go

@@ -22,6 +22,7 @@ import (
 	"github.com/pingcap/dm/dm/config"
 	"github.com/pingcap/dm/pkg/conn"
 	tcontext "github.com/pingcap/dm/pkg/context"
+	"github.com/pingcap/dm/pkg/log"
 	"github.com/pingcap/dm/pkg/terror"
 
 	"go.uber.org/zap"
@@ -296,8 +297,14 @@ func (cp *RemoteCheckPoint) Init(filename string, endPos int64) error {
 
 // Close implements CheckPoint.Close
 func (cp *RemoteCheckPoint) Close() {
-	cp.conn.Close()
-	cp.db.Close()
+	err := cp.conn.Close()
+	if err != nil {
+		cp.tctx.L().Error("close checkpoint connection error", log.ShortError(err))
+	}
+	err = cp.db.Close()
+	if err != nil {
+		cp.tctx.L().Error("close checkpoint db error", log.ShortError(err))
+	}
 }
 
 // GenSQL implements CheckPoint.GenSQL

loader/loader.go

@@ -559,7 +559,10 @@ func (l *Loader) Close() {
 	}
 
 	l.stopLoad()
-	l.toDB.Close()
+	err := l.toDB.Close()
+	if err != nil {
+		l.tctx.L().Error("close toDB error", log.ShortError(err))
+	}
 	l.checkPoint.Close()
 	l.closed.Set(true)
 }

syncer/checkpoint.go

@@ -498,7 +498,11 @@ func (cp *RemoteCheckPoint) createTable() error {
 func (cp *RemoteCheckPoint) Load() error {
 	query := fmt.Sprintf("SELECT `cp_schema`, `cp_table`, `binlog_name`, `binlog_pos`, `is_global` FROM `%s`.`%s` WHERE `id`='%s'", cp.schema, cp.table, cp.id)
 	rows, err := cp.dbConn.querySQL(cp.tctx, query)
-	defer rows.Close()
+	defer func() {
+		if rows != nil {
+			rows.Close()
+		}
+	}()
 
 	failpoint.Inject("LoadCheckpointFailed", func(val failpoint.Value) {
 		err = tmysql.NewErr(uint16(val.(int)))