update

lib/src/util/selector.dart

@@ -0,0 +1,17 @@
+import 'package:file_picker/file_picker.dart';
+
+Future<String?> openFolderPicker(String title) async =>
+    await FilePicker.platform.getDirectoryPath(dialogTitle: title);
+
+Future<String?> openFilePicker(String extension) async {
+  var result = await FilePicker.platform.pickFiles(
+      type: FileType.custom,
+      allowMultiple: false,
+      allowedExtensions: [extension]
+  );
+  if(result == null || result.files.isEmpty){
+    return null;
+  }
+
+  return result.files.first.path;
+}