server: tiny refactor, more go style (#11478)

executor/insert_common.go

@@ -447,7 +447,6 @@ func (e *InsertValues) fillColValue(ctx context.Context, datum types.Datum, idx
 // fillRow fills generated columns, auto_increment column and empty column.
 // For NOT NULL column, it will return error or use zero value based on sql_mode.
 func (e *InsertValues) fillRow(ctx context.Context, row []types.Datum, hasValue []bool) ([]types.Datum, error) {
-	gIdx := 0
 	gCols := make([]*table.Column, 0)
 	for i, c := range e.Table.Cols() {
 		var err error
@@ -466,12 +465,9 @@ func (e *InsertValues) fillRow(ctx context.Context, row []types.Datum, hasValue
 			}
 		}
 	}
-	for _, gCol := range gCols {
-		var err error
-		var val types.Datum
+	for i, gCol := range gCols {
 		colIdx := gCol.ColumnInfo.Offset
-		val, err = e.GenExprs[gIdx].Eval(chunk.MutRowFromDatums(row).ToRow())
-		gIdx++
+		val, err := e.GenExprs[i].Eval(chunk.MutRowFromDatums(row).ToRow())
 		if e.filterErr(err) != nil {
 			return nil, err
 		}

server/server.go

@@ -121,9 +121,8 @@ type Server struct {
 
 // ConnectionCount gets current connection count.
 func (s *Server) ConnectionCount() int {
-	var cnt int
 	s.rwlock.RLock()
-	cnt = len(s.clients)
+	cnt := len(s.clients)
 	s.rwlock.RUnlock()
 	return cnt
 }
@@ -294,7 +293,6 @@ func (s *Server) loadTLSCertificates() {
 		Certificates: []tls.Certificate{tlsCert},
 		ClientCAs:    certPool,
 		ClientAuth:   clientAuthPolicy,
-		MinVersion:   0,
 	}
 }
 
@@ -471,11 +469,9 @@ func (cc *clientConn) connectInfo() *variable.ConnectionInfo {
 		ClientPort:        cc.peerPort,
 		ServerID:          1,
 		ServerPort:        int(cc.server.cfg.Port),
-		Duration:          0,
 		User:              cc.user,
 		ServerOSLoginUser: osUser,
 		OSVersion:         osVersion,
-		ClientVersion:     "",
 		ServerVersion:     mysql.TiDBReleaseVersion,
 		SSLVersion:        "v1.2.0", // for current go version
 		PID:               serverPID,