go语言学习例子No.38-简单的并发下载

package main

import (
	"fmt"
	"io"
	"net/http"
	"os"
	"sync"
)

type Resource struct {
	Filename string
	Url      string
}
type DownLoad struct {
	Resources []Resource
	Dir       string
	wg        *sync.WaitGroup
}

func main() {

	d := NewDownload("./")
	d.AppendResource("1.zip", "http://192.168.1.50:5000/api/v3/file/get/96/Etcher_V1.5.70_XiTongZhiJia.zip?sign=f9hI4r4KXjCwew9J5l2Xvcia8CAd4FQc_qxBA_Kczg4%3D%3A0")
	d.AppendResource("2.exe", "http://192.168.1.50:5000/api/v3/file/get/97/JDSoft_SurfMill8.0_X64_Pro_Setup.exe?sign=V7d4TW1HzZhWcBQj_MtNyVD4BonhsMpVTN6yzJ7iZyY%3D%3A0")
	d.Start()

}
func NewDownload(dir string) *DownLoad {
	return &DownLoad{
		Dir: dir,
		wg:  &sync.WaitGroup{},
	}

}
func (d *DownLoad) AppendResource(filename, url string) {
	d.Resources = append(d.Resources, Resource{
		Filename: filename,
		Url:      url,
	})

}
func (d *DownLoad) Start() {
	for _, v := range d.Resources {
		d.wg.Add(1)
		go download(v, d.wg)
	}
	d.wg.Wait()

}

func download(r Resource, wg *sync.WaitGroup) {
	req, err := http.NewRequest("GET", r.Url, nil)
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		fmt.Println("Get失败", err)
	}
	defer resp.Body.Close()
	// fileSize, _ := strconv.Atoi(resp.Header.Get("Content-Length"))
	// fmt.Println("filesize:", fileSize)
	file, err := os.Create(r.Filename)
	defer file.Close()
	if err != nil {
		fmt.Println("创建文件失败", err)
	}
	_, err = io.Copy(file, resp.Body)
	if err != nil {
		fmt.Println("写入文件失败", err)
	}
	fmt.Println(r.Filename, "下载完成！")
	wg.Done()

}