核心中的NTLM身份验证HttpClient

我正在尝试使用HttpClient访问需要NTLM身份验证的REST服务。但是我一直收到401未经授权。我的代码看起来像这样

    private static void Main()
    {
        var uri = new Uri("http://localhost:15001");
        var credentialsCache = new CredentialCache { { uri, "NTLM", CredentialCache.DefaultNetworkCredentials } };
        var handler = new HttpClientHandler { Credentials = credentialsCache };
        var httpClient = new HttpClient(handler) { BaseAddress = uri, Timeout = new TimeSpan(0, 0, 10) };
        httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        var respOnse= httpClient.GetAsync("api/MyMethod").Result;
    }

我的目标框架是netcoreapp2.0。如果我更改为net461，它将正常工作。不确定我在做什么错吗？