v0.3.3 pre

pubspec.yaml

@@ -14,5 +14,7 @@ dependencies:
   common_utils: '>=1.2.1 <3.0.0'
   # https://github.com/Sky24n/sp_util
   sp_util: '>=1.0.0 <3.0.0'
+  # https://github.com/tekartik/synchronized.dart
+  synchronized: '>=1.5.1 <4.0.0'
   # https://github.com/flutter/plugins/tree/master/packages/path_provider
   path_provider: '>=1.2.0 <3.0.0'