Golang context to cancel HTTP request and response

main.go

package main

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"time"
)

func main() {
	//
	ctx, cf := context.WithCancel(context.Background())

	// spawn a new HTTP server which emulates "long" work with 10 seconds timer
	go func() {
		http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			ctx := r.Context()
			fmt.Println("processing request")

			select {
			case <-time.After(10 * time.Second):
				io.WriteString(w, "Hello, world!\n")
			case <-ctx.Done():
				fmt.Println("processing cancelled")
			}
		})

		log.Fatal(http.ListenAndServe(":8080", nil))
	}()

	// We use a simliest one approach to spawn a server without a way to be
	// aknowledge
	time.Sleep(1 * time.Second)

	fmt.Println("we are all set")

	// spawn a new worker with a request to fetch a page from the server
	go func() {
		client := http.DefaultClient
		req, _ := http.NewRequest("GET", "http://localhost:8080", nil)

		// Assign the context to the request
		req = req.WithContext(ctx)

		// Perform a request
		res, err := client.Do(req)

		fmt.Printf("%T:%+v\n", res, res)
		fmt.Printf("%T:%+v\n", err, err)
	}()

	// Wait 3 seconds and cancel the request
	time.Sleep(3 * time.Second)
	fmt.Println("It's time to cancel request")
	cf()

	fmt.Scanln()