Refactor library order.

lib/main.dart

@@ -1,3 +1,4 @@
+import 'dart:io';
 import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:geolocator/geolocator.dart';
@@ -8,8 +9,6 @@ import 'package:timezone/timezone.dart' as tz;
 import 'package:http/http.dart' as http;
 import 'dart:convert';
 
-import 'dart:io';
-
 void main() async {
   WidgetsFlutterBinding.ensureInitialized();
   tz.initializeTimeZones();