Remove Lambda runtime workarounds

Remove the need to use reflection to set the HttpClient.
Throw OperationCanceledException instead of returning a dummy response.

src/AwsLambdaTestServer/RuntimeHandler.cs

@@ -129,11 +129,7 @@ internal async Task HandleNextAsync(HttpContext httpContext)
                     "Stopped listening for additional requests for Lambda function with ARN {FunctionArn}.",
                     _options.FunctionArn);
 
-                // Send a dummy response to prevent the listen loop from erroring
-                request = new LambdaTestRequest(new[] { (byte)'{', (byte)'}' }, "xx-lambda-test-server-stopped-xx");
-
-                // This dummy request wasn't enqueued, so it needs manually adding
-                _responses.GetOrAdd(request.AwsRequestId, (_) => Channel.CreateBounded<LambdaTestResponse>(1));
+                throw;
             }
 
             // Write the response for the Lambda runtime to pass to the function to invoke

tests/AwsLambdaTestServer.Tests/FunctionRunner.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache 2.0 license. See the LICENSE file in the project root for full license information.
 
 using System.Net.Http;
-using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
 using Amazon.Lambda.RuntimeSupport;
@@ -19,17 +18,7 @@ internal static async Task RunAsync<T>(HttpClient httpClient, CancellationToken
             var serializer = new JsonSerializer();
 
             using var handlerWrapper = HandlerWrapper.GetHandlerWrapper<MyRequest, MyResponse>(handler.SumAsync, serializer);
-            using var bootstrap = new LambdaBootstrap(handlerWrapper, handler.InitializeAsync);
-
-            if (httpClient != null)
-            {
-                // Replace the internal runtime API client with one using the specified HttpClient.
-                // See https://github.com/aws/aws-lambda-dotnet/blob/4f9142b95b376bd238bce6be43f4e1ec1f983592/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs#L41
-                var client = new RuntimeApiClient(httpClient);
-
-                var property = typeof(LambdaBootstrap).GetProperty("Client", BindingFlags.Instance | BindingFlags.NonPublic);
-                property.SetValue(bootstrap, client);
-            }
+            using var bootstrap = new LambdaBootstrap(httpClient, handlerWrapper, handler.InitializeAsync);
 
             await bootstrap.RunAsync(cancellationToken);
         }

tests/AwsLambdaTestServer.Tests/LambdaTestServerTests.cs

@@ -347,6 +347,29 @@ void Configure(IServiceCollection services)
             }
         }
 
+        [Fact]
+        public async Task Function_Returns_If_No_Requests_Within_Timeout()
+        {
+            // Arrange
+            void Configure(IServiceCollection services)
+            {
+                services.AddLogging((builder) => builder.AddXUnit(this));
+            }
+
+            using var server = new LambdaTestServer(Configure);
+            using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(2));
+
+            await server.StartAsync(cts.Token);
+
+            using var httpClient = server.CreateClient();
+
+            // Act
+            await MyFunctionEntrypoint.RunAsync(httpClient, cts.Token);
+
+            // Assert
+            cts.IsCancellationRequested.ShouldBeTrue();
+        }
+
         [Fact]
         public void Finalizer_Does_Not_Throw()
         {