start method
Starts data transfer.
Implementation
@override
Future<Stream<DataBody>> start(State state) async {
logger?.info('worker: Sending data request...');
DataRange? range = state.transferred > 0
? DataRange(state.transferred, state.head.size - 1)
: null;
var resp = await _conn.get(state.head.url, range: range);
var bufferedStream = bufferedListStream(resp.stream, bufferSize);
return bufferedStream.map((s) => DataBody(s));
}