fix: minor potential bug squash in the case that local addr is invalid

main.go

@@ -25,52 +25,59 @@ var (
 	addr      = flag.String("addr", ":8080", "the address to listen on in the case of a local listener")
 )
 
+// redirectToTLS is a simple http hander that redirects all HTTP requests to HTTPs.
 func redirectToTLS(w http.ResponseWriter, r *http.Request) {
 	newURL := fmt.Sprintf("https://%s%s", r.Host, r.RequestURI)
 	http.Redirect(w, r, newURL, http.StatusMovedPermanently)
 }
 
+// serveLocal sets up a local TCP listener on the specified addr, and then serves the embedded
+// filesystem over HTTP on the given listener.
 func serveLocal(files fs.FS, addr string) {
-	var httpLn net.Listener
+	a, err := net.ResolveTCPAddr("tcp", addr)
+	if err != nil {
+		slog.Error(err.Error())
+		os.Exit(1)
+	}
 
-	if a, err := net.ResolveTCPAddr("tcp", addr); err == nil {
-		httpLn, err = net.ListenTCP("tcp", a)
-		if err != nil {
-			slog.Error(err.Error())
-			os.Exit(1)
-		}
+	httpLn, err := net.ListenTCP("tcp", a)
+	if err != nil {
+		slog.Error(err.Error())
+		os.Exit(1)
 	}
+
 	slog.Info(fmt.Sprintf("started HTTP listener on %s", addr))
 
 	// Serve an HTTP file server using our embedded filesystem
 	slog.Info("starting file server for web ui")
-	err := http.Serve(httpLn, http.FileServer(http.FS(files)))
+	err = http.Serve(httpLn, http.FileServer(http.FS(files)))
 	if err != nil {
 		slog.Error(err.Error())
 		os.Exit(1)
 	}
 }
 
+// serveTailscale sets up HTTP & HTTPs listeners on the tailnet and serves the embedded FS on them.
 func serveTailscale(files fs.FS) {
 	tsLogger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{}))
 
-	s := &tsnet.Server{
+	tsnetServer := &tsnet.Server{
 		Hostname: *hostname,
 		Logf: func(msg string, args ...any) {
 			l := tsLogger.With(slog.String("source", "tsnet"), slog.String("hostname", *hostname))
 			l.Info(fmt.Sprintf(msg, args...))
 		},
 	}
-	defer s.Close()
+	defer tsnetServer.Close()
 
 	if !*tsnetLogs {
-		s.Logf = func(string, ...any) {}
+		tsnetServer.Logf = func(string, ...any) {}
 		slog.Warn("tsnet logs are disabled, interactive auth link will not be shown")
 	}
 
 	// Start a standard HTTP server in the background to redirect HTTP -> HTTPS
 	go func() {
-		httpLn, err := s.Listen("tcp", ":80")
+		httpLn, err := tsnetServer.Listen("tcp", ":80")
 		if err != nil {
 			slog.Error(err.Error())
 			os.Exit(1)
@@ -85,7 +92,7 @@ func serveTailscale(files fs.FS) {
 		}
 	}()
 
-	tlsLn, err := s.ListenTLS("tcp", ":443")
+	tlsLn, err := tsnetServer.ListenTLS("tcp", ":443")
 	if err != nil {
 		slog.Error(err.Error())
 		os.Exit(1)