A Google Cloud Function that fetches 10 remote resources concurrently

concurrent.go

package p

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

func Concurrent(w http.ResponseWriter, r *http.Request) {
	titles := []string{
		"New_York_City",
		"San_Francisco",
		"Miami",
		"Los_Angeles",
		"Moscow",
		"Tokyo",
		"London",
		"Berlin",
		"Sao_Paulo",
		"Lagos",
	}

	t := time.Now()
	var wg sync.WaitGroup
	wg.Add(len(titles))
	for _, title := range titles {
		title := title
		go func() {
			fetch(title)
			wg.Done()
		}()
	}
	wg.Wait()
	log.Println("Fetched", len(titles), "resources in", time.Since(t))
}

func fetch(title string) {
	log.Println("START fetch", title)
	// Foil caches
	trailer := fmt.Sprintf("?foil=%d", rand.Intn(9999))
	u := "https://en.wikipedia.org/api/rest_v1/page/summary/" + title + trailer
	res, err := http.Get(u)
	if err != nil {
		log.Println("Error fetching: ", err)
	}
	buffer, err := ioutil.ReadAll(res.Body)
	res.Body.Close()
	if err != nil {
		log.Println("Error reading body: ", err)
	}
	_ = buffer
	log.Println("END fetch", title, "->", len(buffer), "bytes")
}