在学习爬虫的时候，需要进行分页爬取，于是我就提前访问了一次以便获取相应页的总页数，使用了goroutines,但是爬取效率反而变慢了，还出现卡死的情况，谁能帮我看看是怎么回事？

获取城市代码：

package parser

import (
	"crawler/engine"
	"crawler/fetcher"
	"fmt"
	"github.com/PuerkitoBio/goquery"
	"log"
	"regexp"
	"strconv"
	"strings"
)

var numRe = regexp.MustCompile(`\d+`)

func ParseCity(contents []byte) engine.ParseResult {

	dom, err := goquery.NewDocumentFromReader(strings.NewReader(string(contents)))
	if err != nil {
		log.Fatalln(err)
	}
	var list []string
	dom.Find(".groupForum .topicTitle").Each(func(i int, selection *goquery.Selection) {
		_, exists := selection.Attr("span")
		var (
			href string
			e    bool
		)
		if exists {
			href, e = selection.Find(".topicTitleSelf a").Attr("href")
		} else {
			href, e = selection.Find("a").Attr("href")
		}

		if e {
			list = append(list, href)
		}
	})

	arr := make(chan map[string]string, 100)
	flag := make(chan bool, 1)
	for _, uri := range list {
		go func(uri string) {
			contents, err := fetcher.Fetch(uri)
			if err != nil {
				flag <- false
			}
			//获取分页
			doc, err := goquery.NewDocumentFromReader(strings.NewReader(string(contents)))
			if err != nil {
				flag <- false
			}
			size := dom.Find(".pagejump").Size()

			total := 1
			if size > 1 {
				var page string
				doc.Find(".page-number").Each(func(i int, selection *goquery.Selection) {
					page = selection.Text()
				})
				total, _ = strconv.Atoi(numRe.FindString(page))
			}
			arr <- map[string]string{"total": strconv.Itoa(total), "href": uri}
		}(uri)
	}

	var r = make(chan engine.ParseResult,100)
	go func() {
		for {
			select {
			case f := <-flag:
				if !f {
					continue
				}
			case body := <-arr:
				var result engine.ParseResult
				//t, _ := strconv.Atoi(body["total"])
				u := body["href"]
				result.Requests = append(result.Requests, engine.Request{
					Url: u,
					//ParseFunc: func(contents []byte) engine.ParseResult {
					//	return ParseProfile(contents, u, t)
					//},
				})
			}
		}
	}()

	for {
		select {
		case result:= <-r:
			fmt.Printf("城市：%+v\n\r",result)
			return result
		}
	}

}

是否是for循环一直在等待的原因？如果是，应该怎么处理呢？