Golang错误处理与性能优化实战

var ErrNotFound = errors.New("resource not found")

func Find(id string) (*Item, error) {
    if !exists(id) {
        return nil, ErrNotFound
    }
    // ...
}

if err := readConfig(); err != nil {
    return fmt.Errorf("failed to read config: %w", err)
}

g, ctx := errgroup.WithContext(context.Background())
g.SetLimit(10) // 控制最大并发

for _, url := range urls {
    url := url
    g.Go(func() error {
        select {
        case <-ctx.Done():
            return ctx.Err()
        default:
        }

        resp, err := http.Get(url)
        if err != nil {
            return fmt.Errorf("fetch %s: %w", url, err)
        }
        defer resp.Body.Close()
        // 处理响应
        return nil
    })
}

if err := g.Wait(); err != nil {
    log.Printf("Request failed: %v", err)
}

var errorCount uint64

func handleError(err error) {
    count := atomic.AddUint64(&errorCount, 1)
    if count%1000 == 0 {
        log.Printf("Encountered %d errors, last: %v", count, err)
    }
}