NullReferenceException: Object reference not set to an instance of an object.

   at Gremlin.Net.Driver.Connection.ReceiveAsync[T]()
   at Gremlin.Net.Driver.Connection.SubmitAsync[T](RequestMessage requestMessage)
   at Gremlin.Net.Driver.ProxyConnection.SubmitAsync[T](RequestMessage requestMessage)
   at Gremlin.Net.Driver.GremlinClient.SubmitAsync[T](RequestMessage requestMessage)
   at Gremlin.Net.Driver.GremlinClientExtensions.SubmitAsync[T](IGremlinClient gremlinClient, String requestScript, Dictionary`2 bindings)

private static string database = "db";
    private static string collection = "col";
    private static string hostname = "grem-test.gremlin.cosmosdb.azure.com";
    public void test()
    {
        var gremlinServer = new GremlinServer(hostname, 443, enableSsl: true,
                                                username: "/dbs/" + database + "/colls/" + collection,
                                                password: authKey);
        var gremlinClient = new GremlinClient(gremlinServer);
        var grem = "g.V()";
        var t = gremlinClient.SubmitAsync<dynamic>(grem);
        t.Wait();

        foreach (var result in t.Result)
        {
            // The vertex results are formed as dictionaries with a nested dictionary for their properties
            string output = JsonConvert.SerializeObject(result);
            Console.WriteLine(String.Format("tResult:nt{0}", output));
        }