Workaround for https://github.com/ChilliCream/graphql-platform/issues/6698

src/Tgstation.Server.Host/Core/Application.cs

@@ -56,6 +56,7 @@ using Tgstation.Server.Host.Controllers.Results;
 using Tgstation.Server.Host.Database;
 using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.GraphQL;
+using Tgstation.Server.Host.GraphQL.Subscriptions;
 using Tgstation.Server.Host.GraphQL.Types;
 using Tgstation.Server.Host.GraphQL.Types.Interceptors;
 using Tgstation.Server.Host.GraphQL.Types.Scalars;
@@ -295,6 +296,7 @@ namespace Tgstation.Server.Host.Core
 			// configure graphql
 			if (postSetupServices.InternalConfiguration.EnableGraphQL)
 				services
+					.AddScoped<ITopicEventReceiver, ShutdownAwareTopicEventReceiver>()
 					.AddGraphQLServer()
 					.AddAuthorization()
 					.ModifyOptions(options =>

src/Tgstation.Server.Host/GraphQL/Subscription.cs

@@ -38,7 +38,7 @@ namespace Tgstation.Server.Host.GraphQL
 		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
 		/// <returns>A <see cref="ValueTask{TResult}"/> resulting in a <see cref="ISourceStream{TMessage}"/> of the <see cref="SessionInvalidationReason"/> for the <paramref name="authenticationContext"/>.</returns>
 		public ValueTask<ISourceStream<SessionInvalidationReason>> SessionInvalidatedStream(
-			[Service] ITopicEventReceiver receiver,
+			[Service] HotChocolate.Subscriptions.ITopicEventReceiver receiver, // Intentionally not using our override here, topic callers are built to explicitly handle cases of server shutdown
 			[Service] ISessionInvalidationTracker invalidationTracker,
 			[Service] IAuthenticationContext authenticationContext,
 			CancellationToken cancellationToken)

src/Tgstation.Server.Host/GraphQL/Subscriptions/ITopicEventReceiver.cs

@@ -0,0 +1,9 @@
+namespace Tgstation.Server.Host.GraphQL.Subscriptions
+{
+	/// <summary>
+	/// Implementation of <see cref="HotChocolate.Subscriptions.ITopicEventReceiver"/> that works around the <see cref="global::System.Threading.CancellationToken"/> issue described in https://github.com/ChilliCream/graphql-platform/issues/6698.
+	/// </summary>
+	public interface ITopicEventReceiver : HotChocolate.Subscriptions.ITopicEventReceiver
+	{
+	}
+}

src/Tgstation.Server.Host/GraphQL/Subscriptions/ShutdownAwareTopicEventReceiver.cs

@@ -0,0 +1,89 @@
+using System;
+using System.Collections.Concurrent;
+using System.Threading;
+using System.Threading.Tasks;
+
+using HotChocolate.Execution;
+using HotChocolate.Subscriptions;
+
+using Microsoft.Extensions.Hosting;
+
+namespace Tgstation.Server.Host.GraphQL.Subscriptions
+{
+	/// <inheritdoc cref="ITopicEventReceiver" />
+	sealed class ShutdownAwareTopicEventReceiver : ITopicEventReceiver, IAsyncDisposable
+	{
+		/// <summary>
+		/// The <see cref="IHostApplicationLifetime"/> for the <see cref="ShutdownAwareTopicEventReceiver"/>.
+		/// </summary>
+		readonly IHostApplicationLifetime hostApplicationLifetime;
+
+		/// <summary>
+		/// The wrapped <see cref="HotChocolate.Subscriptions.ITopicEventReceiver"/>.
+		/// </summary>
+		readonly HotChocolate.Subscriptions.ITopicEventReceiver hotChocolateReceiver;
+
+		/// <summary>
+		/// A <see cref="ConcurrentBag{T}"/> of <see cref="CancellationTokenRegistration"/>s that were created for this scope.
+		/// </summary>
+		readonly ConcurrentBag<CancellationTokenRegistration> registrations;
+
+		/// <summary>
+		/// A <see cref="ConcurrentBag{T}"/> of <see cref="ValueTask"/>s returned from initiating <see cref="IAsyncDisposable.DisposeAsync"/> calls on <see cref="ISourceStream"/>s.
+		/// </summary>
+		readonly ConcurrentBag<Task> disposeTasks;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="ShutdownAwareTopicEventReceiver"/> class.
+		/// </summary>
+		/// <param name="hostApplicationLifetime">The value of <see cref="hostApplicationLifetime"/>.</param>
+		/// <param name="hotChocolateReceiver">The value of <see cref="hotChocolateReceiver"/>.</param>
+		public ShutdownAwareTopicEventReceiver(
+			IHostApplicationLifetime hostApplicationLifetime,
+			HotChocolate.Subscriptions.ITopicEventReceiver hotChocolateReceiver)
+		{
+			this.hostApplicationLifetime = hostApplicationLifetime ?? throw new ArgumentNullException(nameof(hostApplicationLifetime));
+			this.hotChocolateReceiver = hotChocolateReceiver ?? throw new ArgumentNullException(nameof(hotChocolateReceiver));
+
+			registrations = new ConcurrentBag<CancellationTokenRegistration>();
+			disposeTasks = new ConcurrentBag<Task>();
+		}
+
+		/// <inheritdoc />
+		public async ValueTask DisposeAsync()
+		{
+			foreach (var registration in registrations)
+			{
+				registration.Dispose();
+			}
+
+			await Task.WhenAll(disposeTasks);
+		}
+
+		/// <inheritdoc />
+		public ValueTask<ISourceStream<TMessage>> SubscribeAsync<TMessage>(string topicName, CancellationToken cancellationToken)
+			=> WrapWithApplicationLifetimeCancellation(
+				hotChocolateReceiver.SubscribeAsync<TMessage>(topicName, cancellationToken));
+
+		/// <inheritdoc />
+		public ValueTask<ISourceStream<TMessage>> SubscribeAsync<TMessage>(string topicName, int? bufferCapacity, TopicBufferFullMode? bufferFullMode, CancellationToken cancellationToken)
+			=> WrapWithApplicationLifetimeCancellation(
+				hotChocolateReceiver.SubscribeAsync<TMessage>(topicName, bufferCapacity, bufferFullMode, cancellationToken));
+
+		/// <summary>
+		/// Wraps a given <paramref name="sourceStreamTask"/> with <see cref="hostApplicationLifetime"/> cancellation awareness.
+		/// </summary>
+		/// <typeparam name="TMessage">The <see cref="Type"/> of message.</typeparam>
+		/// <param name="sourceStreamTask">The result of a call to the <see cref="hotChocolateReceiver"/>.</param>
+		/// <returns>The result of <paramref name="sourceStreamTask"/> with lifetime aware cancellation.</returns>
+		async ValueTask<ISourceStream<TMessage>> WrapWithApplicationLifetimeCancellation<TMessage>(ValueTask<ISourceStream<TMessage>> sourceStreamTask)
+		{
+			var sourceStream = await sourceStreamTask;
+			registrations.Add(
+				hostApplicationLifetime.ApplicationStopping.Register(
+					() => disposeTasks.Add(
+						sourceStream.DisposeAsync().AsTask())));
+			return sourceStream;
+		}
+	}
+}

src/Tgstation.Server.Host/GraphQL/Subscriptions/UserSubscriptions.cs

@@ -5,7 +5,6 @@ using System.Threading.Tasks;
 
 using HotChocolate;
 using HotChocolate.Execution;
-using HotChocolate.Subscriptions;
 using HotChocolate.Types;
 using HotChocolate.Types.Relay;