asynchronicity in Go

Recently, I talked about asynchronous page loads in Perl three different ways (using AnyEvent, Mojolicious, and HTTP::Async).  Commenters fixed the Mojo example and added an IO::Lambda example. Another poster created a Perl 6 example.

Today, I did it in Go, which has concurrency built in to the language. That is, no special modules are needed to load the pages asynchronously;  if we wrote a program to load the pages one after another instead, the import lines would be the same. 

package main

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

func loadpage (url string, c chan<- string) {
    start := time.Now()
    response, error := http.Get(url)
    if error != nil {
        c <- fmt.Sprintln(error)
        return
    }
    length, _ := io.Copy(ioutil.Discard, response.Body)
    response.Body.Close()
    c <- fmt.Sprintf("%-25s has length %8d and loaded in %.2f s\n",
                     url, length, time.Since(start).Seconds())
}

func main() {
    urls := []string{
        "https://www.google.com",
        "http://www.windley.com/",
        "https://www.bing.com",
        "http://www.example.com",
        "http://www.wetpaint.com",
        "http://www.uh.cu",
    }

    start := time.Now()

    c := make(chan string)

    for _, url := range urls {
        go loadpage(url, c)
    }

    for i := range urls {
        fmt.Print(i, " ", <-c)
    }

    fmt.Printf("Total elapsed time %.2f s\n",
               time.Since(start).Seconds())
}

Running this gives

$ go run apl.go
0 Get https://www.bing.com: certificate is valid for a248.e.akamai.net,
*.akamaihd.net, *.akamaihd-staging.net, not www.bing.com
1 https://www.google.com    has length    12400 and loaded in 1.01 s
2 http://www.windley.com/   has length    50178 and loaded in 1.04 s
3 http://www.wetpaint.com   has length    74952 and loaded in 1.06 s
4 http://www.example.com    has length     2966 and loaded in 1.09 s
5 http://www.uh.cu          has length    57304 and loaded in 2.97 s
Total elapsed time 2.97 s

Nice! I'm still new at Go, but so far I really like it.