Improve server shutdown

Less likely to corrupt data now.

main.go

@@ -66,16 +66,16 @@ func main() {
 	})
 
 	server := &http.Server{Addr: listenAddr}
-	go func() {
-		if err := http.ListenAndServe(listenAddr, nil); err != nil &&
-			err != http.ErrServerClosed {
-			log.Fatalln(err)
-		}
-	}()
+	errs := make(chan error, 1)
+	go func() { errs <- server.ListenAndServe() }()
 
 	sig := make(chan os.Signal)
 	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
-	<-sig
+	select {
+	case <-sig:
+	case err := <-errs:
+		log.Println(err)
+	}
 
 	// For simplicity, we'll wait for everything to finish, including snapshots.
 	if err := server.Shutdown(context.Background()); err != nil {