public Task RunAsync(Action <CrawlerResult> result)
=> Task.Run(() => result(CrawlerResult.Ref(
_context.HttpClient.Send(_context.Request)
.OnError(Fail(result))
.OnSuccess(r => TaskResult <Stream> .Wait(r.Content.ReadAsStreamAsync()).ForResult())
.OnSuccess(r => _context.HtmlLoader.Load(r.Value))
.OnSuccess(r => ToElement(r.Value)))));
private Action <Exception> Fail(Action <CrawlerResult> callback) => ex => callback(CrawlerResult.Fail(ex));
