SingleGetterDataSource<Type, Param> class abstract

Implement this abstract in your data source if it can fetch some data. Note that 1 class can implements from multiple abstracts.

class GetParams {
  final String token;
}

class SessionDataSource implements
  SingleGetterDataSource<Session, GetParams> {

  final HttpClient client;

  const SessionDataSource({required this.client});

  @override
  FutureOr<Session> readOne({GetParams params}) async {
    /// Perform client.get() or something.
  }
}

If you can live with less type safety, you can simply use Map<String,dynamic> as Param.

Instead of throwing an exception, you should return Left instead.