How to handle optimistic lock in go

main.go

package main

import (
	"database/sql"

	"github.com/gin-gonic/gin"
	_ "github.com/go-sql-driver/mysql"
)

var db *sql.DB

func init() {
	var err error
	db, err = sql.Open("mysql", "root:root@tcp(localhost:3306)/demo")
	if err != nil {
		panic(err)
	}

	if err := db.Ping(); err != nil {
		panic(err)
	}
}

func main() {
	r := gin.Default()

	r.POST("/employees/:id/update", func(c *gin.Context) {
		id := c.Param("id")
		newName := c.DefaultPostForm("name", "")

		tx, err := db.Begin()
		if err != nil {
			c.JSON(500, gin.H{
				"error": err,
			})
			return
		}
		defer tx.Rollback()

		var oldName string
		row := tx.QueryRow("SELECT name FROM employees WHERE id=?", id)
		if err := row.Scan(&oldName); err != nil {
			c.JSON(400, gin.H{
				"error": err,
			})
			return
		}

		if oldName == newName {
			c.JSON(200, gin.H{
				"status": "success",
			})
			return
		}

		result, err := tx.Exec("UPDATE employees SET name=? WHERE id=? AND name=?", newName, id, oldName)
		if err != nil {
			c.JSON(400, gin.H{
				"error": err,
			})
			return
		}
		affected, err := result.RowsAffected()
		if err != nil {
			c.JSON(400, gin.H{
				"error": err,
			})
			return
		}
		if affected != 1 {
			c.JSON(400, gin.H{
				"error": "Optimistic lock failed",
			})
			return
		}

		if err := tx.Commit(); err != nil {
			c.JSON(400, gin.H{
				"error": err,
			})
			return
		}

		c.JSON(200, gin.H{
			"status": "success",
		})
	})

	r.Run()
}