c# - C# HttpClient to socks4/5 プロキシ?

Question

次のコードで http プロキシを設定できます。

public class CustomFlurlHttpClient : DefaultHttpClientFactory {
    public override HttpClient CreateClient(Url url, HttpMessageHandler m) {
        return base.CreateClient(url, CreateProxyHttpClientHandler("http://192.168.0.103:9090"));
    }

    private HttpClientHandler CreateProxyHttpClientHandler(string proxyUrl, string user = "", string passw = "") {
        NetworkCredential proxyCreds = null;
        var proxyUri = new Uri(proxyUrl);
        proxyCreds = new NetworkCredential (user, passw);
        var proxy = new WebProxy (proxyUri, false) {
            UseDefaultCredentials = false,
            Credentials = proxyCreds
        };
        var clientHandler = new HttpClientHandler {
            UseProxy = true,
            Proxy = proxy,
            PreAuthenticate = true,
            UseDefaultCredentials = false
        };
        if (user != "" && passw != "") {
            clientHandler.Credentials = new NetworkCredential (user, passw);
        }
        return clientHandler;
    }
}
class MainClass {
    public static void Main (string[] args) {
        run ();
        Console.ReadKey ();
    }

    async static void run() {
        using(FlurlClient client = new FlurlClient(c => { c.HttpClientFactory = new CustomFlurlHttpClient();})) {
            var result = await client.WithUrl("https://www.google.com").GetStringAsync();
            Console.WriteLine(result);
        };
    }
}

ソックスプロキシではありません。それを行う方法はありますか？または、非同期/待機構文がサポートされている他の(非推奨ではない)残りのクライアント?