feat: Add force parameter to close method for immediate shutdown

lib/src/adapter/adapter.dart

@@ -98,7 +98,12 @@ abstract class Adapter {
   ///
   /// For example, for an HTTP server adapter, this might close the underlying
   /// server socket.
-  Future<void> close();
+  ///
+  /// If [force] is true, the adapter will immediately close all connections
+  /// and shut down without waiting for in-flight requests to complete.
+  /// If [force] is false (the default), the adapter will wait for all
+  /// in-flight requests to finish before shutting down.
+  Future<void> close({final bool force = false});
 
   ConnectionsInfo get connectionsInfo;
 }

lib/src/adapter/io/io_adapter.dart

@@ -99,7 +99,7 @@ class IOAdapter extends Adapter {
   }
 
   @override
-  Future<void> close() => _server.close();
+  Future<void> close({final bool force = false}) => _server.close(force: force);
 
   @override
   ConnectionsInfo get connectionsInfo {

lib/src/relic_server.dart

@@ -18,7 +18,12 @@ sealed class RelicServer {
   Future<void> mountAndStart(final Handler handler);
 
   /// Close the server
-  Future<void> close();
+  ///
+  /// If [force] is true, the server will immediately close all connections
+  /// and shut down without waiting for in-flight requests to complete.
+  /// If [force] is false (the default), the server will wait for all
+  /// in-flight requests to finish before shutting down.
+  Future<void> close({final bool force = false});
 
   /// Returns information about the current connections.
   Future<ConnectionsInfo> connectionsInfo();
@@ -65,9 +70,9 @@ final class _RelicServer implements RelicServer {
   }
 
   @override
-  Future<void> close() async {
+  Future<void> close({final bool force = false}) async {
     await _stopListening();
-    await (await _adapter).close();
+    await (await _adapter).close(force: force);
     _port = null;
   }
 
@@ -196,8 +201,8 @@ final class _IsolatedRelicServer extends IsolatedObject<RelicServer>
     : super(() => RelicServer(adapterFactory));
 
   @override
-  Future<void> close() async {
-    await evaluate((final r) => r.close());
+  Future<void> close({final bool force = false}) async {
+    await evaluate((final r) => r.close(force: force));
     await super.close();
     _port = null;
   }
@@ -230,10 +235,10 @@ final class _MultiIsolateRelicServer implements RelicServer {
       );
 
   @override
-  Future<void> close() async {
+  Future<void> close({final bool force = false}) async {
     final children = List.of(_children);
     _children.clear();
-    await children.map((final c) => c.close()).wait;
+    await children.map((final c) => c.close(force: force)).wait;
   }
 
   @override

test/relic_server_graceful_shutdown_test.dart

@@ -231,6 +231,58 @@ void main() {
         expect(response.statusCode, HttpStatus.ok);
       }
     });
+
+    test(
+      'when server.close(force: true) is called with in-flight requests, '
+      'then server shuts down immediately without waiting for requests',
+      () async {
+        final (:responseFutures, :canComplete) = await _startInFlightRequests(
+          server,
+        );
+
+        // Close the server forcefully while requests are in-flight
+        await server.close(force: true);
+
+        // The server should close immediately, even though requests are blocked
+        // Now allow the requests to try to complete
+        canComplete.complete();
+
+        // Wait for all responses - they should fail or be incomplete
+        final results = await Future.wait(
+          responseFutures.map(
+            (final f) => f.then<http.Response?>(
+              (final r) => r,
+              onError: (final Object e) => null,
+            ),
+          ),
+        );
+
+        // At least some requests should have failed due to forced closure
+        // (exact behavior may vary based on timing, but we expect errors)
+        final failedCount = results.where((final r) => r == null).length;
+        expect(
+          failedCount,
+          greaterThan(0),
+          reason: 'Some requests should fail when force closing',
+        );
+      },
+    );
+
+    test(
+      'when server.close(force: true) is called on idle server, '
+      'then server closes immediately',
+      () async {
+        await server.mountAndStart(
+          (final req) => Response.ok(body: Body.fromString('OK')),
+        );
+
+        // Close an idle server with force
+        await expectLater(
+          server.close(force: true),
+          completes,
+        );
+      },
+    );
   });
 
   group('Given a RelicServer with multi-isolate configuration', () {

test/router/relic_app_test.dart

@@ -133,5 +133,5 @@ class _FakeAdapter extends Fake implements Adapter {
   late int port = Random().nextInt(65536);
 
   @override
-  Future<void> close() async {}
+  Future<void> close({final bool force = false}) async {}
 }