Future _copyDatabase() async {
    final String databasePath = await getDatabasesPath();
    final String path = join(databasePath, 'dic.db');
    final File file = File(path);
    if (!file.existsSync()) {
      ByteData data = await rootBundle.load(join('assets', 'dic.db'));
      List bytes = data.buffer.asUint8List(data.offsetInBytes, data.lengthInBytes);
      await file.writeAsBytes(bytes, flush: true);
      logger.i('database successfully copied to $path');
    } else {
      logger.i('database already exist');
    }
  }