Result.cs

private async Task<Result<T>> Send<T>(string urlSuffix, Func<HttpContent, T> responseParser)
{
    try
    {
        var answer = await SendInternal(urlSuffix);
        if (answer.IsSuccessStatusCode)
        {
            return Result.Ok(responseParser(answer.Content));
        }
        else
        {
            return Result.Fail<T>($"HttpRequest failed with code: {answer.StatusCode}");
        }
    }
    catch (AggregateException ex) when (ex.InnerExceptions.Any(e => e is TaskCanceledException))
    {
        return Result.Fail<T>("HttpRequest was cancelled");
    }
}

private async Task<Result> Send(string urlSuffix)
{
    try
    {
        var answer = await SendInternal(urlSuffix);
        if (answer.IsSuccessStatusCode)
        {
            return Result.Ok();
        }
        else
        {
            return Result.Fail($"HttpRequest failed with code: {answer.StatusCode}");
        }
    }
    catch (AggregateException ex) when (ex.InnerExceptions.Any(e => e is TaskCanceledException))
    {
        return Result.Fail("HttpRequest was cancelled");
    }
}

private async Task<HttpResponseMessage> SendInternal(string urlSuffix)
{
    var cts = new CancellationTokenSource();
    _pendingRequests.Add(cts);
    var answer = await _client.GetAsync(_uriBase + urlSuffix, cts.Token);
    _pendingRequests.Remove(cts);
    return answer;
}