http server handle req context

http_slow_server.go

package main

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

func slowRespHandler(w http.ResponseWriter, r *http.Request) {

	fmt.Println("start handle request")
	defer fmt.Println("end handle request")

	for i := 0; i < 15; i++ {

		time.Sleep(time.Duration(1) * time.Second)

		// test incoming request context before writing anything
		// From the doc:
		// "For incoming server requests, the context is canceled when the client's connection closes, the request is canceled (with HTTP/2), or when the ServeHTTP method returns"
		select {
		case <-r.Context().Done():
			fmt.Println("error: request context done, does nothing")
			return
		default:
		}

	}

	fmt.Printf("send foobar\n")

	_, err := fmt.Fprintf(w, "foobar\n")
	if err != nil {
		log.Fatal("error:", err)
	}

	fmt.Printf("sent foobar\n")

}

func main() {

	mux := http.NewServeMux()
	mux.HandleFunc("/slowresp", slowRespHandler)

	srv := &http.Server{
		Addr: ":8080",
		ConnState: func(conn net.Conn, event http.ConnState) {
			// log the connection state
			log.Printf("addr: %s, changed state to: %s", conn.RemoteAddr(), event.String())
		},
		Handler: mux,
	}

	log.Fatal(srv.ListenAndServe())
}

http_timeout_client.go

package main

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

func main() {
	tmOutCtx, cancel := context.WithTimeout(context.Background(), time.Duration(2)*time.Second)

	req, _ := http.NewRequestWithContext(tmOutCtx, "GET", "http://localhost:8080/slowresp", nil)
	defer cancel()

	println("Do request")

	client := http.Client{}
	resp, err := client.Do(req)
	if err != nil {
		panic(err)
	}

	bodyBytes, err := ioutil.ReadAll(resp.Body)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println(string(bodyBytes))

}