ctxcancel.go

package main

import (
	"context"
	"fmt"
	"net/http"
	"time"

	"github.com/felixge/httpsnoop"
	"github.com/go-chi/chi"
)

func main() {
	r := chi.NewRouter()

	r.With(middleware).Get("/", root)

	http.ListenAndServe(":8080", r)
}

func root(w http.ResponseWriter, r *http.Request) {
	err := longRun(r.Context())
	if err != nil {
		fmt.Println("error:", err)
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}

	w.WriteHeader(200)
}

func longRun(ctx context.Context) error {
	c := make(chan bool)
	go func() {
		time.Sleep(3 * time.Minute)
		c <- true
	}()

	select {
	case <-ctx.Done():
		return ctx.Err()
	case <-c:
		return nil
	}
}

func middleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		m := httpsnoop.CaptureMetrics(next, w, r)
		fmt.Println("metrics: ", m)
	})
}