🐛 Fix types

lib/src/fluwx.dart

@@ -129,17 +129,17 @@ class Fluwx {
 
   /// Unsubscribe responses from WeChat
   @Deprecated("use [removeSubscriber] instead")
-  unsubscribeResponse(WeChatResponseSubscriber listener) {
+  void unsubscribeResponse(WeChatResponseSubscriber listener) {
     removeSubscriber(listener);
   }
 
   /// remove your subscriber from WeChat
-  removeSubscriber(WeChatResponseSubscriber listener) {
+  void removeSubscriber(WeChatResponseSubscriber listener) {
     _responseListeners.remove(listener);
   }
 
   /// remove all existing
-  clearSubscribers() {
+  void clearSubscribers() {
     _responseListeners.clear();
   }
 }

lib/src/foundation/cancelable.dart

@@ -17,20 +17,19 @@
  * the License.
  */
 
-import '../response/wechat_response.dart';
+import 'package:flutter/foundation.dart';
 
-typedef WeChatResponseSubscriber = Function(WeChatResponse response);
 mixin FluwxCancelable {
-  cancel();
+  void cancel();
 }
 
 class FluwxCancelableImpl implements FluwxCancelable {
-  final Function onCancel;
+  const FluwxCancelableImpl({required this.onCancel});
 
-  FluwxCancelableImpl({required this.onCancel});
+  final VoidCallback onCancel;
 
   @override
-  cancel() {
+  void cancel() {
     onCancel();
   }
 }

lib/src/response/wechat_response.dart

@@ -22,6 +22,7 @@ import 'dart:typed_data';
 const String _errCode = 'errCode';
 const String _errStr = 'errStr';
 
+typedef WeChatResponseSubscriber = void Function(WeChatResponse response);
 typedef _WeChatResponseInvoker = WeChatResponse Function(Map argument);
 
 Map<String, _WeChatResponseInvoker> _nameAndResponseMapper = {