fixed #421

Tests/MQTTnet.AspNetCore.Tests/Mockups/ConnectionContextMockup.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using System.IO.Pipelines;
+using Microsoft.AspNetCore.Connections;
+using Microsoft.AspNetCore.Http.Features;
+
+namespace MQTTnet.AspNetCore.Tests.Mockups
+{
+    public class ConnectionContextMockup : ConnectionContext
+    {
+        public override string ConnectionId { get; set; }
+
+        public override IFeatureCollection Features { get; }
+
+        public override IDictionary<object, object> Items { get; set; }
+        public override IDuplexPipe Transport { get; set; }
+
+        public ConnectionContextMockup()
+        {
+            //Transport = new DefaultConnectionContext
+        }
+    }
+}