add a parameter to mc.Begin and reuse it.

Author: shogo82148

connection.go

@@ -82,11 +82,20 @@ func (mc *mysqlConn) handleParams() (err error) {
 }
 
 func (mc *mysqlConn) Begin() (driver.Tx, error) {
+	return mc.begin(false)
+}
+
+func (mc *mysqlConn) begin(readOnly bool) (driver.Tx, error) {
 	if mc.closed.IsSet() {
 		errLog.Print(ErrInvalidConn)
 		return nil, driver.ErrBadConn
 	}
-	err := mc.exec("START TRANSACTION")
+	var err error
+	if readOnly {
+		err = mc.exec("START TRANSACTION READ ONLY")
+	} else {
+		err = mc.exec("START TRANSACTION")
+	}
 	if err == nil {
 		return &mysqlTx{mc}, err
 	}

connection_go18.go

@@ -56,23 +56,7 @@ func (mc *mysqlConn) BeginTx(ctx context.Context, opts driver.TxOptions) (driver
 		}
 	}
 
-	if opts.ReadOnly {
-		return mc.beginReadOnly()
-	}
-	return mc.Begin()
-}
-
-func (mc *mysqlConn) beginReadOnly() (driver.Tx, error) {
-	if mc.closed.IsSet() {
-		errLog.Print(ErrInvalidConn)
-		return nil, driver.ErrBadConn
-	}
-	err := mc.exec("START TRANSACTION READ ONLY")
-	if err != nil {
-		return nil, err
-	}
-
-	return &mysqlTx{mc}, nil
+	return mc.begin(opts.ReadOnly)
 }
 
 func (mc *mysqlConn) QueryContext(ctx context.Context, query string, args []driver.NamedValue) (driver.Rows, error) {