延时任务模拟

策略一：

1. 服务器进行分布式部署；
2. 接口通过乐观锁机制实时处理扣费/加钱等操作（如：UPDATE user SET amount = amount - ${amount} WHERE id = ${user_id} AND amount - ${amount} > 0）；
3. 某些非关键操作，如礼物统计、榜单更新等，全部通过消息队列异步完成；
4. 对于连续高频的打赏行为，采用批量写入策略（客户端进行延时控制），减轻实时压力

策略二：
通过单点服务器进行延时控制

 package main
 import (
     "fmt"
     "log"
     "math/rand"
     "net/http"
     "sync"
     "time"
 )
 type UserCount struct {
     timer *time.Timer
     count int
 }
 var mapUserCount = map[int]UserCount{}
 var mu sync.Mutex
 /// 思路: 通过 time.AfterFunc 处理延时任务
 func delay(w http.ResponseWriter, r *http.Request) {
     mu.Lock()
     defer mu.Unlock()
     rand.Seed(time.Now().Unix())
     userId := rand.Intn(3)
     timeout := time.Second
     userCount, ok := mapUserCount[userId]
     if ok {
         fmt.Fprintln(w, "ok")
         userCount.count++
         userCount.timer.Reset(timeout) // 更新计时器
     } else {
         fmt.Fprintln(w, "not ok")
         userCount.count = 1
         userCount.timer = time.AfterFunc(timeout, func() { // 新建计时器
             totalCount := mapUserCount[userId].count
             fmt.Println("userId:", userId, ", total count:", totalCount, ", key deleted.")
             // todo: 业务逻辑部分
             // ...
             delete(mapUserCount, userId) // 删除 key
         })
     }
     mapUserCount[userId] = userCount
     // todo: 发送 IM 推送消息
     fmt.Fprintln(w, "userId:", userId)
     fmt.Fprintln(w, "userCount:", userCount)
 }
 func main() {
     http.HandleFunc("/", delay)
     err := http.ListenAndServe(":8080", nil)
     if err != nil {
         log.Fatal("ListenAndServe: ", err)
     }
 }