An example of server shutdown from handler func.

what-if-shutdown-from-handler.go

package main

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

func main() {
	server := &http.Server{}
	mux := http.NewServeMux()
	idleConnsClosed := make(chan struct{})
	shutdown := func() {
		log.Printf("shutdown")
		ctx, canc := context.WithTimeout(context.Background(), 2*time.Second)
		defer canc()
		if err := server.Shutdown(ctx); err != nil {
			log.Printf("shutdown: %s", err)
		} else {
			log.Println("shutdown: ok")
		}
		time.Sleep(10 * time.Second)
		log.Printf("ok, waited")
		close(idleConnsClosed)
	}
	mux.HandleFunc("/stopAsync", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("stop handler")
		fmt.Fprint(w, "stop handler")
		go shutdown()
	})
	mux.HandleFunc("/stop", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("stop handler")
		fmt.Fprint(w, "stop handler")
		shutdown()
	})
	server.Handler = mux
	server.Addr = ":8080"
	if err := server.ListenAndServe(); err != nil {
		log.Printf("err: %s\n", err)
		if err == http.ErrServerClosed {
			log.Println("wait for shutdown to end")
			<-idleConnsClosed
		}
	}
	log.Printf("done")
}