CloudFunction to gather multiple GET requests

gather.go

package p

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"strings"
	"sync"

	"go.uber.org/ratelimit"
)

func Gather(w http.ResponseWriter, r *http.Request) {
	rl := ratelimit.New(100) 
	urlParams := r.URL.Query().Get(("urls"))
	if len(urlParams) == 0 {
		fmt.Fprintf(w, "missing urls param")
		return
	}
	sURLs := strings.Split(urlParams, ",")
	m := sync.Map{}
	wg := &sync.WaitGroup{}
	for _, s := range sURLs {
		rl.Take()
		wg.Add(1)
		go func(sURL string) {
			log.Printf("calling url: %s\n", sURL)
			defer func() {
				log.Printf("done with url: %s\n", sURL)
				wg.Done()
			}()
			resp, err := http.Get(sURL)
			if err != nil {
				log.Printf("%v", err)
				return
			}
			defer resp.Body.Close()

			body, err := ioutil.ReadAll(resp.Body)
			if err != nil {
				log.Printf("%v", err)
				return
			}
			var asJSON map[string]interface{}
			err = json.Unmarshal(body, &asJSON)
			if err != nil {
				log.Printf("%v", err)
				return
			}
			m.Store(sURL, asJSON)
		}(s)
	}

	wg.Wait()

	ret := map[string]interface{}{}

	for _, s := range sURLs {
		if v, ok := m.Load(s); ok {
			data := v.(map[string]interface{})
			ret[s] = data
		}
	}

	v, err := json.Marshal(ret)
	if err != nil {
		log.Printf("%v", err)
		return
	}

	fmt.Fprintf(w, "%s", string(v))
}