Fixing deadlock hang in test when running in single threaded environment

Author: JunTaoLuo

src/Microsoft.AspNet.TestHost/ClientHandler.cs

@@ -94,7 +94,7 @@ protected override async Task<HttpResponseMessage> SendAsync(
                     }
                 });
 
-            return await state.ResponseTask;
+            return await state.ResponseTask.ConfigureAwait(false);
         }
 
         private class RequestState

test/Microsoft.AspNet.TestHost.Tests/TestServerTests.cs

@@ -353,7 +353,7 @@ public async Task DisposedServerThrows()
 
         [ConditionalFact]
         [FrameworkSkipCondition(RuntimeFrameworks.Mono, SkipReason = "Hangs randomly (issue #507)")]
-        public void CancelAborts()
+        public async Task CancelAborts()
         {
             TestServer server = TestServer.Create(app =>
             {
@@ -365,7 +365,7 @@ public void CancelAborts()
                 });
             });
 
-            Assert.Throws<AggregateException>(() => { string result = server.CreateClient().GetStringAsync("/path").Result; });
+            await Assert.ThrowsAsync<TaskCanceledException>(async () => { string result = await server.CreateClient().GetStringAsync("/path"); });
         }
 
         [ConditionalFact]