Add server support for multiple listen addresses

doh-server/server.go

@@ -75,10 +75,27 @@ func (s *Server) Start() error {
 	if s.conf.Verbose {
 		servemux = handlers.CombinedLoggingHandler(os.Stdout, servemux)
 	}
-	if s.conf.Cert != "" || s.conf.Key != "" {
-		return http.ListenAndServeTLS(s.conf.Listen, s.conf.Cert, s.conf.Key, servemux)
+	listeners := make(chan error, len(s.conf.Listen))
+	for _, addr := range s.conf.Listen {
+		if s.conf.Cert != "" || s.conf.Key != "" {
+			go func() {
+				listeners <- http.ListenAndServeTLS(addr, s.conf.Cert, s.conf.Key, servemux)
+			}()
+			continue
+		}
+		go func() {
+			listeners <- http.ListenAndServe(addr, servemux)
+		}()
 	}
-	return http.ListenAndServe(s.conf.Listen, servemux)
+	// wait for all handlers
+	for i := 0; i < cap(listeners); i++ {
+		err := <-listeners
+		if err != nil {
+			return err
+		}
+	}
+	close(listeners)
+	return nil
 }
 
 func (s *Server) handlerFunc(w http.ResponseWriter, r *http.Request) {