Add extra headers param to mg_ws_upgrade()

examples/websocket-server/main.c

@@ -21,7 +21,7 @@ static void fn(struct mg_connection *c, int ev, void *ev_data, void *fn_data) {
     if (mg_http_match_uri(hm, "/websocket")) {
       // Upgrade to websocket. From now on, a connection is a full-duplex
       // Websocket connection, which will receive MG_EV_WS_MSG events.
-      mg_ws_upgrade(c, hm);
+      mg_ws_upgrade(c, hm, NULL);
     } else if (mg_http_match_uri(hm, "/rest")) {
       // Serve REST response
       mg_http_reply(c, 200, "", "{\"result\": %d}\n", 123);