mysql在InnoDB引擎中的锁

    for i := 0;i<300;i++{
        i := i
        go func(i int){
            if err := model.UpdateTest();err != nil{
                fmt.Println(err)
            }

            fmt.Println("current num:" + strconv.Itoa(i))
        }(i)
    }
    time.Sleep(time.Second*5)

func  UpdateTest() error{

    return DB.Self.Exec("update class set num = num -1 where  id = 1 and (num -1 ) >= 0").Error

}