runtime: [HttpClient] SSL Idn decode failure

The following produces an exception:

using System.Net.Http;
using System.Threading.Tasks;

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            HttpClient client = new HttpClient();
            var _ = client.GetAsync("https://r6---sn-uxanug5-hxay.gvt1.com/test/").Result;

        }
    }
}

Stacktrace:

Unhandled Exception: System.AggregateException: One or more errors occurred. (The SSL connection could not be established, see inner exception.) ---> System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception. ---> System.Security.Authentication.AuthenticationException: Authentication failed, see inner exception. ---> System.ArgumentException: Decoded string is not a valid IDN name.
Parameter name: unicode
   at System.Globalization.IdnMapping.GetAsciiCore(String unicodeString, Char* unicode, Int32 count)
   at System.Globalization.IdnMapping.GetAscii(String unicode, Int32 index, Int32 count)
   at Interop.OpenSsl.AllocateSslContext(SslProtocols protocols, SafeX509Handle certHandle, SafeEvpPKeyHandle certKeyHandle, EncryptionPolicy policy, SslAuthenticationOptions sslAuthenticationOptions)
   at System.Net.Security.SafeDeleteSslContext..ctor(SafeFreeSslCredentials credential, SslAuthenticationOptions sslAuthenticationOptions)
   at System.Net.Security.SslStreamPal.HandshakeInternal(SafeFreeCredentials credential, SafeDeleteContext& context, SecurityBuffer inputBuffer, SecurityBuffer outputBuffer, SslAuthenticationOptions sslAuthenticationOptions)
   --- End of inner exception stack trace ---
   at System.Net.Security.SslState.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, ExceptionDispatchInfo exception)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Net.Security.SslStream.BeginAuthenticateAsClient(SslClientAuthenticationOptions sslClientAuthenticationOptions, CancellationToken cancellationToken, AsyncCallback asyncCallback, Object asyncState)
   at System.Net.Security.SslStream.<>c.<AuthenticateAsClientAsync>b__47_0(SslClientAuthenticationOptions arg1, CancellationToken arg2, AsyncCallback callback, Object state)
   at System.Threading.Tasks.TaskFactory`1.FromAsyncImpl[TArg1,TArg2](Func`5 beginMethod, Func`2 endFunction, Action`1 endAction, TArg1 arg1, TArg2 arg2, Object state, TaskCreationOptions creationOptions)
   at System.Threading.Tasks.TaskFactory.FromAsync[TArg1,TArg2](Func`5 beginMethod, Action`1 endMethod, TArg1 arg1, TArg2 arg2, Object state, TaskCreationOptions creationOptions)
   at System.Threading.Tasks.TaskFactory.FromAsync[TArg1,TArg2](Func`5 beginMethod, Action`1 endMethod, TArg1 arg1, TArg2 arg2, Object state)
   at System.Net.Security.SslStream.AuthenticateAsClientAsync(SslClientAuthenticationOptions sslClientAuthenticationOptions, CancellationToken cancellationToken)
   at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
   --- End of inner exception stack trace ---
   at System.Net.Http.ConnectHelper.EstablishSslConnectionAsyncCore(Stream stream, SslClientAuthenticationOptions sslOptions, CancellationToken cancellationToken)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at System.Net.Http.HttpConnectionPool.CreateConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at System.Net.Http.HttpConnectionPool.WaitForCreatedConnectionAsync(ValueTask`1 creationTask)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at test.Program.Main(String[] args) in /tmp/test/Program.cs:line 18

Additional Info

$ dotnet --info
.NET Core SDK (reflecting any global.json):
 Version:   2.1.300-rc1-008673
 Commit:    f5e3ddbe73

Runtime Environment:
 OS Name:     debian
 OS Version:  
 OS Platform: Linux
 RID:         debian-x64
 Base Path:   /usr/share/dotnet/sdk/2.1.300-rc1-008673/

Host (useful for support):
  Version: 2.1.0-rc1
  Commit:  eb9bc92051

.NET Core SDKs installed:
  2.1.300-rc1-008673 [/usr/share/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.0-rc1-final [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.0-rc1-final [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 2.1.0-rc1 [/usr/share/dotnet/shared/Microsoft.NETCore.App]

[EDIT] Add C# syntax highlighting by @karelz