fix: Added runGuardedErrorValidation.

packages/katana/lib/katana.dart

@@ -9,6 +9,7 @@
 library katana;
 
 // Dart imports:
+import 'dart:async';
 import 'dart:convert';
 import 'dart:core' as core;
 import 'dart:core';

packages/katana/lib/src/functions.dart

@@ -160,3 +160,30 @@ bool jsonEncodable(Object? o) {
   }
   return o is num || o is bool || o is String;
 }
+
+/// Verify errors including Async.
+///
+/// The process that raises an Exception is passed to [process], and [onError] is passed what to do when the Exception is raised.
+///
+/// Asyncを含むエラーの検証を行います。
+///
+/// [process]にExceptionを発生させる処理を渡し、[onError]にはExceptionが発生した場合の処理を渡します。
+Future<void> runGuardedErrorValidation(
+  FutureOr<void> Function() process,
+  void Function(Object error, StackTrace stackTrace) onError,
+) async {
+  Completer<void>? completer = Completer();
+  runZonedGuarded(
+    () async {
+      await process();
+      completer?.completeError("Should not be here");
+      completer = null;
+    },
+    (error, stack) {
+      completer?.complete();
+      completer = null;
+      onError(error, stack);
+    },
+  );
+  await completer?.future;
+}