Using GoRoutines

go_routines.go

package main

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

func main() {
	start := time.Now()
	ch := make(chan string) // created a channel
	for _, urls := range os.Args[1:] {
		go fetch(urls, ch) // staring a go routine
	}
	for range os.Args[1:] {
		fmt.Println(<-ch) // fetch data from go routine through channel
	}
	fmt.Printf("%2fs elapsed\n", time.Since(start).Seconds())
}

func fetch(url string, ch chan<- string) {
	start := time.Now()
	resp, err := http.Get(url)

	if err != nil {
		ch <- fmt.Sprint(err) // send error message to channel
		return
	}

	nbytes, err := io.Copy(ioutil.Discard, resp.Body)
	resp.Body.Close()
	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)
}