Golang并发下载文件教程

func downloadFile(url, filename string) error {
    resp, err := http.Get(url)
    if err != nil {
        return err
    }
    defer resp.Body.Close()
<pre class="brush:php;toolbar:false;">file, err := os.Create(filename)
if err != nil {
    return err
}
defer file.Close()

io.Copy(file, resp.Body)
return nil

}

func main() { urls := []string{"http://example.com/file1", "http://example.com/file2"} var wg sync.WaitGroup

for i, url := range urls {
    wg.Add(1)
    go func(u string, idx int) {
        defer wg.Done()
        err := downloadFile(u, fmt.Sprintf("file_%d", idx))
        if err != nil {
            log.Printf("下载失败: %s, 错误: %v", u, err)
        }
    }(url, i)
}
wg.Wait()

}

semaphore := make(chan struct{}, 10) // 最多10个并发
for i, url := range urls {
    go func(u string, idx int) {
        semaphore 

ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
defer cancel()
<p>req, _ := http.NewRequestWithContext(ctx, "GET", url, nil)
resp, err := http.DefaultClient.Do(req)</p>