update dart code

Author: IoTServ

networking.md

@@ -130,8 +130,8 @@ class _MyHomePageState extends State<MyHomePage> {
       var request = await httpClient.getUrl(Uri.parse(url));
       var response = await request.close();
       if (response.statusCode == HttpStatus.OK) {
-        var json = await response.transform(UTF8.decoder).join();
-        var data = JSON.decode(json);
+        var json = await response.transform(utf8.decoder).join();
+        var data = jsonDecode(json);
         result = data['origin'];
       } else {
         result =