Async parallel calls to invoke two APIs using anonymous goroutine functions and channels to pipe the response

main.go

package main

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

	"github.com/julienschmidt/httprouter"
)

func doGet(url string) ([]byte, error) {
	req, err := http.NewRequest("GET", url, nil)
	if err != nil {
		return []byte{}, fmt.Errorf("Failed to create HTTP Request %s", err)
	}

	var getClient = &http.Client{
		Timeout: time.Second * 10,
	}

	resp, err := getClient.Do(req)
	if err != nil {
		return []byte{}, fmt.Errorf("The HTTP request failed with error %s", err)
	}
	defer resp.Body.Close()

	body, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		return []byte{}, fmt.Errorf("Cannot raed response body due to %s", err)
	}
	if 200 != resp.StatusCode {
		return body, fmt.Errorf("HTTP Status Not_OK %s", err)
	}

	return body, nil
}

func formURL(id string) string {
	return fmt.Sprintf("https://jsonplaceholder.typicode.com/todos/%s", id)
}

func GetTodos(id string) []map[string]interface{} {

	//create an empty response of string type
	resp := []map[string]interface{}{}

	//step 1: create channels which can be used to pass a string around
	//(Channels are the pipes that connect concurrent goroutines)
	//Channels are typed by the values they convey.
	chn := make(chan map[string]interface{}, 2)
	errCh := make(chan error, 2)

	//two parallel calls
	go consumeRequest(id, chn, errCh)
	go consumeRequest(id, chn, errCh)

	//ading up the contents of the channels which are string
	for i := 0; i < 2; i++ {
		select {
		case err := <-errCh:
			fmt.Println(err)
		case r := <-chn:
			resp = append(resp, r)
		}
	}

	return resp

}

func consumeRequest(id string, out chan<- map[string]interface{}, errCh chan<- error) {
	body, err := doGet(formURL(id))
	if err != nil {
		errCh <- err
		return
	}
	r := map[string]interface{}{}
	if err := json.Unmarshal(body, &r); err != nil {
		errCh <- err
		return
	}
	out <- r
}

func TodosHandler(writer http.ResponseWriter, req *http.Request, param httprouter.Params) {
	id := param.ByName("id")
	res := GetTodos(id)

	json.NewEncoder(writer).Encode(res)
}

func main() {
	//creates a new router
	router := httprouter.New()

	router.GET("/todos/:id", TodosHandler)

	log.Fatal(http.ListenAndServe(":9093", router))
}