Go: How to Run an HTTP Server Correctly

http_server.go

package main

import (
	"context"
	"embed"
	"html/template"
	"log"
	"log/slog"
	"net"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"
)

var (
	//go:embed templates
	templatesFs embed.FS
	templates   = template.Must(template.ParseFS(templatesFs, "*.html"))
)

func main() {
	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer cancel()
	if err := run(ctx, "", 8080); err != nil {
		log.Fatal(err)
	}
}

func run(ctx context.Context, host string, port int) error {
	addr := net.JoinHostPort(host, strconv.Itoa(port))
	root := http.NewServeMux()
	root.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if err := templates.ExecuteTemplate(w, "landing.html", nil); err != nil {
			slog.Error("ExecuteTemplate failed", "name", "landing.html", "err", err)
		}
	})
	s := &http.Server{
		Addr:    addr,
		Handler: root,
	}
	errCh := make(chan error, 1)
	go func() { errCh <- s.ListenAndServe() }()
	select {
	case err := <-errCh:
		return err
	case <-ctx.Done():
		slog.Info("Shutdown called")
		defer slog.Info("Shutdown returned")
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		return s.Shutdown(shutdownCtx)
	}
}