Increase timeout to fix mac bot (#417)

test/test_with_coverage_test.dart

diff --git a/test/test_with_coverage_test.dart b/test/test_with_coverage_test.dart
index 5aab793..ccde401 100644
--- a/test/test_with_coverage_test.dart
+++ b/test/test_with_coverage_test.dart
@@ -2,6 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+@Timeout(Duration(seconds: 60))
+
 import 'dart:convert';
 import 'dart:io';