fix(dart_frog): Request/Response headers should be Map<String, String> (#217)

Author: felangel

packages/dart_frog/lib/src/request.dart

@@ -102,7 +102,8 @@ class Request {
   Uri get uri => _request.requestedUri;
 
   /// The HTTP headers with case-insensitive keys.
-  Map<String, dynamic> get headers => _request.headers;
+  /// The returned map is unmodifiable.
+  Map<String, String> get headers => _request.headers;
 
   /// The [HttpMethod] associated with the request.
   HttpMethod get method {

packages/dart_frog/lib/src/response.dart

@@ -54,7 +54,8 @@ class Response {
   int get statusCode => _response.statusCode;
 
   /// The HTTP headers with case-insensitive keys.
-  Map<String, dynamic> get headers => _response.headers;
+  /// The returned map is unmodifiable.
+  Map<String, String> get headers => _response.headers;
 
   /// Returns a [Stream] representing the body.
   Stream<List<int>> bytes() => _response.read();

packages/dart_frog/test/src/hot_reload_test.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:io';
 
 import 'package:dart_frog/dart_frog.dart';
@@ -6,16 +7,20 @@ import 'package:test/test.dart';
 void main() {
   group('hotReload', () {
     test('completes', () async {
+      final completer = Completer<void>();
       var invoked = false;
       HttpServer? server;
 
       Future<HttpServer> initializer() async {
         invoked = true;
-        return server = await serve((_) => Response(), 'localhost', 8080);
+        server = await serve((_) => Response(), 'localhost', 8080);
+        completer.complete();
+        return server!;
       }
 
       expect(() => hotReload(initializer), returnsNormally);
-      await Future<void>.delayed(const Duration(seconds: 1));
+
+      await completer.future;
 
       expect(invoked, isTrue);
       expect(server, isNotNull);