go语言 grequests+goquery 简单爬虫，使用多协程并发爬取

/*下载工具*/
package main

import (
"fmt"
//go语言版本的jquery
"github.com/PuerkitoBio/goquery"
"os"
"sync"
"strings"
//go语言版本的request
"github.com/levigross/grequests"
"time"
"strconv"
)

var wg sync.WaitGroup

func main() {
now := time.Now()
initalUrls := []string{"http://www.zngirls.com/girl/18071/album/", }
for _, url := range initalUrls {
doc, err := goquery.NewDocument(url)
if err != nil {
fmt.Errorf("下载错误:%#v", err)
os.Exit(-1)
}

doc.Find(".igalleryli_link").Each(func(i int, s *goquery.Selection) {
src, exists := s.Find("img").Attr("src")
fmt.Printf("开始下载影集图片:%v\n", src)
if (exists) {
wg.Add(1)
go func(src string) {
defer wg.Done()

//下载图片
//tryTimes := map[int]int
n := 0
s := strings.Replace(src, "cover/", "", 1)
ss := strings.Split(s, "/")
fm := strings.Join(ss[:len(ss) - 1], "/")
sf0 := fm + "/%d.jpg"
sfn := fm + "/%03d.jpg"

for {
//持续下载
s := ""
if n == 0 {
s = fmt.Sprintf(sf0, n)
} else {
s = fmt.Sprintf(sfn, n)
}

fmt.Printf("准备下载: %v\n", s)
res, _ := grequests.Get(s, &grequests.RequestOptions{
//结构体可以对指定的类型给值，而不一定都赋值
Headers:map[string]string{
"Referer":"http://www.zngirls.com",
"User-Agent":"Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/50.0.2661.102 Safari/537.36"}})
//条件需要修改，如果没有图片，返回的是盗链，图片4kb
if res.StatusCode != 200 {
fmt.Printf("下载失败，退出影集下载:%s\n", src)
break
}

//图片可能是该网站，返回的盗链图片（4kb左右)
length := res.Header.Get("Content-Length")
slen,_ := strconv.Atoi(length)
if slen < 4100{
fmt.Printf("下载内容失败,退出影集下载:%s\n", src)
break
}

index := strings.Index(s, "gallery")
if index == -1 {
fmt.Errorf("无效地址，找不到gallery关键词，解析失败:%s\n", src)
return
}

ss2 := strings.Split(string(s[index:]), "/")
dirname := strings.Join(ss2[:len(ss2) - 1], "/")
if _, err := os.Stat(dirname); err != nil {
fmt.Printf("创建下载文件夹:%s\n", dirname)
os.MkdirAll(dirname, 0666)
}

filename := strings.Join(ss2, "/")
res.DownloadToFile(filename)
fmt.Printf("成功下载图片到:%s\n", filename)
n++
}
}(src)
}
})
}

wg.Wait()
//4M的带宽下载，需要16m36s，总大小202M,10个文件夹,560个文件
fmt.Printf("下载任务完成，耗时:%#v\n", time.Now().Sub(now))
}