feat: retry before sending (#489)

* feat: retry before sending

* reduce idleTimeout

lib/http/retry_interceptor.dart

@@ -0,0 +1,34 @@
+import 'package:dio/dio.dart';
+
+import 'index.dart';
+
+class RetryInterceptor extends Interceptor {
+  final int _count;
+  final int _delay;
+
+  RetryInterceptor(this._count, this._delay);
+
+  @override
+  void onError(DioException err, ErrorInterceptorHandler handler) {
+    if (err.response != null) return handler.next(err);
+    switch (err.type) {
+      case DioExceptionType.connectionError:
+      case DioExceptionType.connectionTimeout:
+      case DioExceptionType.sendTimeout:
+        if ((err.requestOptions.extra['_rt'] ??= 0) < _count) {
+          Future.delayed(
+              Duration(
+                  milliseconds: ++err.requestOptions.extra['_rt'] * _delay),
+              () => Request.dio
+                  .fetch(err.requestOptions)
+                  .then(handler.resolve)
+                  .onError<DioException>((error, _) => handler.reject(error)));
+        } else {
+          handler.next(err);
+        }
+        return;
+      default:
+        return handler.next(err);
+    }
+  }
+}