1
// WaitGroup 的痛苦写法
2
var wg sync.WaitGroup
3
errChan := make(chan error, 3)
4

5
wg.Add(3)
6
go func() {
7
    defer wg.Done()
8
    if err := callA(); err != nil {
9
        errChan <- err
10
    }
11
}()
12
// ... 重复 3 次
13

14
wg.Wait()
15
close(errChan)
16
for err := range errChan {
17
    // 处理错误
18
}
19

20
// errgroup 的优雅写法
21
g, ctx := errgroup.WithContext(context.Background())
22
g.Go(func() error {
23
    return callA()
24
})
25
// ... 重复 3 次
26

27
if err := g.Wait(); err != nil {
28
    // 处理错误
29
}

1
package main
2

3
import (
4
    "context"
5
    "errors"
6
    "fmt"
7
    "time"
8
    "golang.org/x/sync/errgroup"
9
)
10

11
func SearchData(ctx context.Context, name string, delay time.Duration, willFail bool) (string, error) {
12
    fmt.Printf("🚀 任务 [%s] 开始执行...\n", name)
13
    select {
14
    case <-time.After(delay):
15
        if willFail {
16
            return "", errors.New(name + " 发生故障")
17
        }
18
        return name + " 获取成功", nil
19
    case <-ctx.Done():
20
        fmt.Printf("⏹️ 任务 [%s] 收到取消信号，优雅退出。\n", name)
21
        return "", ctx.Err()
22
    }
23
}
24

25
func main() {
26
    g, ctx := errgroup.WithContext(context.Background())
27
    resultChan := make(chan string, 1) // 缓冲为 1，防止发送者阻塞
28

29
    tasks := []struct {
30
        n string
31
        d time.Duration
32
        f bool
33
    }{
34
        {"Service-A", 3 * time.Second, false},
35
        {"Service-B", 1 * time.Second, true}, // 它最快且报错，会触发全局 cancel
36
        {"Service-C", 5 * time.Second, false},
37
    }
38

39
    for _, t := range tasks {
40
        tt := t // 闭包陷阱：必须进行变量拷贝
41
        g.Go(func() error {
42
            res, err := SearchData(ctx, tt.n, tt.d, tt.f)
43
            if err == nil {
44
                select {
45
                case resultChan <- res:
46
                default:
47
                }
48
            }
49
            return err
50
        })
51
    }
52

53
    go func() {
54
        if err := g.Wait(); err != nil {
55
            fmt.Printf("\n📢 Wait() 最终捕获错误: %v\n", err)
56
        }
57
        close(resultChan)
58
    }()
59

60
    if finalRes, ok := <-resultChan; ok {
61
        fmt.Printf("\n🏆 拿到结果: %s\n", finalRes)
62
    } else {
63
        fmt.Println("\n💀 任务全部失败或被取消。")
64
    }
65
}

1
func GetUserInfo(ctx context.Context, userID string) (*UserInfo, error) {
2
    g, ctx := errgroup.WithContext(ctx)
3
    var info UserInfo
4

5
    g.Go(func() error {
6
        var err error
7
        info.Profile, err = getProfile(ctx, userID)
8
        return err
9
    })
10

11
    g.Go(func() error {
12
        var err error
13
        info.Orders, err = getOrders(ctx, userID)
14
        return err
15
    })
16

17
    g.Go(func() error {
18
        var err error
19
        info.Coupons, err = getCoupons(ctx, userID)
20
        return err
21
    })
22

23
    if err := g.Wait(); err != nil {
24
        return nil, err
25
    }
26

27
    return &info, nil
28
}

1
func HealthCheck(ctx context.Context) error {
2
    g, ctx := errgroup.WithContext(ctx)
3
    g.SetLimit(5)
4

5
    services := []string{"db", "redis", "mq", "cache", "api"}
6

7
    for _, svc := range services {
8
        svc := svc
9
        g.Go(func() error {
10
            return checkService(ctx, svc)
11
        })
12
    }
13

14
    return g.Wait()
15
}