server.go

package main

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

func handlePing(w http.ResponseWriter, r *http.Request) {
	log.Println("ping: Got a request")
	time.Sleep(3 * time.Second)
	fmt.Fprintf(w, "pong")
}

func doSomeWork(data []byte) {
	time.Sleep(5 * time.Second)
}

func handleUserAPI(w http.ResponseWriter, r *http.Request) {
	done := make(chan bool)

	log.Println("I started processing the request")

	req, err := http.NewRequestWithContext(
		r.Context(),
		"GET",
		"http://localhost:8080/ping", nil,
	)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	client := &http.Client{}
	log.Println("Outgoing HTTP request")
	resp, err := client.Do(req)
	if err != nil {
		log.Printf("Error making request: %v\n", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	defer resp.Body.Close()
	data, _ := io.ReadAll(resp.Body)

	log.Println("Processing the response i got")

	go func() {
		doSomeWork(data)
		done <- true
	}()

	select {
	case <-done:
		log.Println("doSomeWork done: Continuing request processing")
	case <-r.Context().Done():
		log.Printf("Aborting request processing: %v\n", r.Context().Err())
		return
	}

	fmt.Fprint(w, string(data))
	log.Println("I finished processing the request")
}

func main() {
	listenAddr := os.Getenv("LISTEN_ADDR")
	if len(listenAddr) == 0 {
		listenAddr = ":8443"
	}

	timeoutDuration := 30 * time.Second

	userHandler := http.HandlerFunc(handleUserAPI)
	hTimeout := http.TimeoutHandler(
		userHandler,
		timeoutDuration,
		"I ran out of time",
	)

	mux := http.NewServeMux()
	mux.Handle("/api/users/", hTimeout)
	mux.HandleFunc("/ping", handlePing)

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