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))
}