Fix Hosting shutdown output subscription race

Co-authored-by: rosebyte <14963300+rosebyte@users.noreply.github.com>

Author: Copilot

src/libraries/Microsoft.Extensions.Hosting/tests/FunctionalTests/IntegrationTesting/src/Deployers/SelfHostDeployer.cs

@@ -20,6 +20,7 @@ public class SelfHostDeployer : ApplicationDeployer
         private const string ApplicationStartedMessage = "Application started. Press Ctrl+C to shut down.";
 
         public Process HostProcess { get; private set; }
+        public event DataReceivedEventHandler OutputReceived;
 
         public SelfHostDeployer(DeploymentParameters deploymentParameters, ILoggerFactory loggerFactory)
             : base(deploymentParameters, loggerFactory)
@@ -130,6 +131,8 @@ protected async Task<CancellationToken> StartSelfHostAsync()
                     {
                         started.TrySetResult(null);
                     }
+
+                    OutputReceived?.Invoke(sender, dataArgs);
                 };
                 var hostExitTokenSource = new CancellationTokenSource();
                 HostProcess.Exited += (sender, e) =>

src/libraries/Microsoft.Extensions.Hosting/tests/FunctionalTests/ShutdownTests.cs

@@ -71,12 +71,10 @@ private async Task ExecuteShutdownTest(string testName, string shutdownMechanic)
 
             using (var deployer = new SelfHostDeployer(deploymentParameters, xunitTestLoggerFactory))
             {
-                var result = await deployer.DeployAsync();
-
                 var started = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
                 var completed = new TaskCompletionSource<int>(TaskCreationOptions.RunContinuationsAsynchronously);
                 var output = string.Empty;
-                deployer.HostProcess.OutputDataReceived += (sender, args) =>
+                deployer.OutputReceived += (sender, args) =>
                 {
                     if (!string.IsNullOrEmpty(args.Data) && args.Data.StartsWith(StartedMessage))
                     {
@@ -94,6 +92,8 @@ private async Task ExecuteShutdownTest(string testName, string shutdownMechanic)
                     }
                 };
 
+                await deployer.DeployAsync();
+
                 await started.Task.WaitAsync(TimeSpan.FromSeconds(180));
 
                 SendShutdownSignal(deployer.HostProcess);