go批量請求URL，計算時間

第一種寫法

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"time"
)

func main()  {
	start :=time.Now()
	ch :=make(chan string)

	var urls = []string{"http://www.baidu.com",
		"http://www.qq.com",
		"http://www.58.com",
		"http://www.0532888.cn",
		"https://www.xin.com",
	}
	for _,url:=range urls[:len(urls)]{
		go fetch(url,ch)
	}

	for range urls[:len(urls)]{
		fmt.Println(<-ch)
	}
	fmt.Printf("%.2fs elapsed \n",time.Since(start).Seconds())

}

func fetch(url string,ch chan<- string){
	start:=time.Now()
	res,err:=http.Get(url)
	if err!=nil{
		ch <- fmt.Sprint(err)
		return
	}
	nbytes,err:=io.Copy(ioutil.Discard,res.Body)
	if err!=nil{
		ch <- fmt.Sprintf("while reading %s:%v",url,err)
		return
	}
	secs:=time.Since(start).Seconds()
	ch <- fmt.Sprintf("%.2fs %7d %s",secs,nbytes,url)

}

第二種寫法

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"sync"
	"time"
)

func main() {
	var urls = []string{"http://www.baidu.com",
		"https://www.qq.com",
		"https://lf.58.com",
		"http://www.0532888.cn",
		"https://www.xin.com",
	}
	start := time.Now()
	wg := sync.WaitGroup{}
	wg.Add(len(urls))
	for _, val := range urls {
		go func(url string) {
			start := time.Now()
			res, err := http.Get(url)
			if err != nil {
				fmt.Println(err)
				return
			}
			nbytes, err := io.Copy(ioutil.Discard, res.Body)
			if err != nil {
				fmt.Printf("while reading %s:%v\n", url, err)
				return
			}
			fmt.Printf("%.2fs %7d %s\n", time.Since(start).Seconds(), nbytes, url)
			wg.Done()
		}(val)
	}

	wg.Wait()

	fmt.Printf("%.2fs elapsed \n", time.Since(start).Seconds())

}

0.12s 156965 http://www.baidu.com
0.26s 51216 http://www.0532888.cn
0.44s 235408 http://www.qq.com
0.51s 63305 https://www.xin.com
0.55s 131536 http://www.58.com
0.55s elapsed