# panic：sync：WaitGroup 在上一次 Wait 返回前被复用

- **ID:** `go/waitgroup-wait-reused-before-return`
- **领域:** go
- **类别:** runtime_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

在另一个 goroutine 仍阻塞在 Wait() 时调用了 Add()，运行时会禁止此操作以防止计数器竞争。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 1.20 | active | — | — |
| 1.21 | active | — | — |
| 1.22 | active | — | — |

## 解决方案

1. **** (95% 成功率)
   ```
   var wg sync.WaitGroup
for i := 0; i < n; i++ { wg.Add(1) }
for i := 0; i < n; i++ {
    go func() { defer wg.Done(); work() }()
}
wg.Wait()
   ```
2. **** (93% 成功率)
   ```
   sem := make(chan struct{}, 10)
var wg sync.WaitGroup
for _, job := range jobs {
    sem <- struct{}{}
    wg.Add(1)
    go func(j Job) {
        defer wg.Done()
        defer func() { <-sem }()
        run(j)
    }(job)
}
wg.Wait()
   ```

## 无效尝试

- **** — Wait() may return before the goroutine even starts, so Add happens after Wait and the counter update races. (80% 失败率)
- **** — Sleep does not synchronize Add with Wait; under load the panic still occurs. (70% 失败率)