go如何利用orm简单实现接口分布式锁

type Participating struct {
 ID   uint     `xorm:"autoincr id" json:"id,omitempty"`
 Openid string    `xorm:"openid" json:"openid"`
 Hit   uint     `xorm:"hit" json:"hit"`
 Orderid string    `xorm:"order_id" json:"order_id"`
 Redpack uint     `xorm:"redpack" json:"redpack"`
 Status uint     `xorm:"status" json:"status"`
 Ctime  tool.JsonTime `xorm:"ctime" json:"ctime,omitempty"`
 Utime  tool.JsonTime `xorm:"utime" json:"utime,omitempty"`
 PayTime tool.JsonTime `xorm:"pay_time" json:"pay_time,omitempty"`
}

p_info := &Participating{}
// 查找具体提现数额
has, _ := db.Dalmore.Where("openid = ? and hit = 1 and status = 0", openid).Get(p_info)
if !has {
 resp.Error(errcode.NO_REDPACK_FOUND, nil, nil)
 return
}

// 改status为提现中
p_info.Status = 2
db.Dalmore.Cols("status").Where("openid = ? and hit = 1 and status = 0", openid).Update(p_info)

// 提现p_info.Redpack

type Set struct {
 m map[string]bool
 sync.RWMutex
}

func New() *Set {
 return &Set{
 m: map[string]bool{},
 }
}

var nodelock = set.New()

// 加锁
nodelock.Lock()

p_info := &Participating{}
// 查找具体提现数额
has, _ := db.Dalmore.Where("openid = ? and hit = 1 and status = 0", openid).Get(p_info)
if !has {
 resp.Error(errcode.NO_REDPACK_FOUND, nil, nil)
 return
}

// 改status为提现中
p_info.Status = 2
db.Dalmore.Cols("status").Where("openid = ? and hit = 1 and status = 0", openid).Update(p_info)

// 释放锁
nodelock.Unlock()

// 提现p_info.Redpack

//记录update修改条数
num, err := db.Dalmore.Cols("status").Where("openid = ? and status = 0 and hit = 1", openid).Update(p_update)
if err != nil {
 logger.Runtime().Debug(map[string]interface{}{"error": err.Error()}, "error while updating")
 resp.Error(errcode.INTERNAL_ERROR, nil, nil)
 return
}

// 查看update操作到底修改了多少条数据，起到了分布式锁的作用
if num != 1 {
 resp.Error(errcode.NO_REDPACK_FOUND, nil, nil)
 return
}

p_info := &Participating{}
_, err := db.Dalmore.Where("openid = ? and status = 2", openid).Get(p_info)
if err != nil {
 logger.Runtime().Debug(map[string]interface{}{"error": err.Error()}, "error while selecting")
 resp.Error(errcode.INTERNAL_ERROR, nil, nil)
 return
}

// 提现p_info.Redpack