WebSockets in ASP.NET Core are easy to use but due to the simple model it's easy to forget that socket requests are long lived and can linger for a long time in the background and that can cause problems when an application needs to shut down cleanly. Luckily there's an `IHostApplicationLifetime` interface available that allows hooking shutdown operations and that provides the necessary cancellation tokens to allow an WebSocket connection to be terminated in response to a shutdown event. This post shows how this works.