Remotely safely shutdown a Go HTTP server

safehttp.go

package main
import "net/http"
import "net"
import "sync"

var lis net.Listener 

func main(){
	var err error
	// make our own listener
	lis, err = net.Listen("tcp",":8080")
	if err != nil {
		panic(err)
	}
	// make our own handler that puts all requests in a wait group.
	h := &handler{ServeMux: http.NewServeMux()}

	// add a close handlefunc to that handler
	h.ServeMux.HandleFunc("/",close)
	
	//listen and serve until listner is closed
	http.Serve(lis,h)

	//wait here until all current requests complete.
	h.w.Wait()	
}
type handler struct {
	w sync.WaitGroup
	*http.ServeMux
}

func (h *handler)ServeHTTP(w http.ResponseWriter, r *http.Request){
	h.w.Add(1)
	defer h.w.Done()
	h.ServeMux.ServeHTTP(w, r)
	
	//important to flush before decrementing the wait group.
	//we won't get a chance to once main() ends.
	w.(http.Flusher).Flush()
}

func close(w http.ResponseWriter, r *http.Request){
	lis.Close()
	w.Write([]byte("closed listener"))
}