Async vs. Sync HTTP requests

sometimes_concurrency_is_good.go

// This tries to show the difference between async and sync
// HTTP GET requests. Big surprise: its way faster do this
// async...
package main

import (
	"fmt"
	"github.com/bentranter/chalk"
	"net/http"
	"time"
)

var urls = []string{
	"https://github.com",
	"https://google.ca",
	"https://twitter.com",
	"http://golang.org",
	"http://ninesummers.com",
	"https://facebook.com",
	"https://yahoo.com",
	"http://metalab.co",
	"https://reddit.com",
	"https://youtube.com",
	"https://amazon.com",
	"https://wikipedia.org",
	"https://linkedin.com",
	"https://bing.com",
	"https://instagram.com",
	"https://microsoft.com",
	"https://msn.com",
	"https://wordpress.com",
	"https://tumblr.com",
}

// HTTPResponse is the struct that holds our response
// data
type HTTPResponse struct {
	url      string
	response *http.Response
	err      error
}

func asyncHTTPGet(urls []string) []*HTTPResponse {
	start := time.Now()
	ch := make(chan *HTTPResponse)
	responses := []*HTTPResponse{}

	for _, url := range urls {
		go func(url string) {
			fmt.Printf("Fetching %s \n", url)
			resp, err := http.Get(url)
			if err != nil {
				fmt.Println("Error: ", err)
			}

			defer resp.Body.Close()
			ch <- &HTTPResponse{url, resp, err}
		}(url)
	}

	for {
		select {
		case r := <-ch:
			fmt.Printf("%s | %s was fetched\n", time.Since(start), r.url)
			responses = append(responses, r)
			if len(responses) == len(urls) {
				return responses
			}
		}
	}

	return responses
}

func syncHTTPGet(urls []string) []*HTTPResponse {
	start := time.Now()
	responses := []*HTTPResponse{}

	for _, url := range urls {

		fmt.Printf("Fetching %s \n", url)
		resp, err := http.Get(url)
		if err != nil {
			fmt.Println("Error: ", err)
		}

		defer resp.Body.Close()
		fmt.Printf("%s | %s was fetched\n", time.Since(start), url)
		responses = append(responses, &HTTPResponse{url, resp, err})
	}

	return responses
}

func main() {

	fmt.Println(chalk.Blue("*** ASYNC ***"))

	results := asyncHTTPGet(urls)
	for _, result := range results {
		fmt.Printf("%s status, %s\n", result.url, result.response.Status)
	}

	fmt.Println(chalk.Blue("\n\n*** SYNC ***"))

	results = syncHTTPGet(urls)
	for _, result := range results {
		fmt.Printf("%s status, %s\n", result.url, result.response.Status)
	}
}

Before anyone points it out: yes, I know that if an HTTP req fails, we'll get that classic error everyone knows and loves panic: runtime error: invalid memory address or nil pointer dereference since I don't break out of the loop at line 48 if the error isn't nil.