feat: direct call download api by cgo dart

ui/flutter/lib/api/native/model/start_config.dart

@@ -0,0 +1,19 @@
+import 'package:json_annotation/json_annotation.dart';
+
+part 'start_config.g.dart';
+
+@JsonSerializable()
+class StartConfig {
+  String storage;
+  String storageDir;
+
+  StartConfig({
+    this.storage = '',
+    this.storageDir = '',
+  });
+
+  factory StartConfig.fromJson(Map<String, dynamic> json) =>
+      _$StartConfigFromJson(json);
+
+  Map<String, dynamic> toJson() => _$StartConfigToJson(this);
+}