Implement IAsyncDisposable from IConnectionMultiplexer (#2161)

Fixes #2160.

We may want to implement `IAsyncDisposable` in more public `IDisposable` classes which can dispose their resources asynchronously.

Co-authored-by: Nick Craver <[email protected]>

Author: kimsey0

docs/ReleaseNotes.md

@@ -3,6 +3,7 @@
 ## Unreleased
 
 - Fix [#2182](https://github.com/StackExchange/StackExchange.Redis/issues/2182): Be more flexible in which commands are "primary only" in order to support users with replicas that are explicitly configured to allow writes ([#2183 by slorello89](https://github.com/StackExchange/StackExchange.Redis/pull/2183))
+- Adds: `IConnectionMultiplexer` now implements `IAsyncDisposable` ([#2161 by kimsey0](https://github.com/StackExchange/StackExchange.Redis/pull/2161))
 
 ## 2.6.48
 

src/StackExchange.Redis/ConnectionMultiplexer.cs

@@ -2016,6 +2016,21 @@ public void Dispose()
             oldTimer?.Dispose();
         }
 
+        /// <summary>
+        /// Release all resources associated with this object.
+        /// </summary>
+        public async ValueTask DisposeAsync()
+        {
+            GC.SuppressFinalize(this);
+            await CloseAsync(!_isDisposed);
+            if (sentinelConnection is ConnectionMultiplexer sentinel)
+            {
+                await sentinel.DisposeAsync();
+            }
+            var oldTimer = Interlocked.Exchange(ref sentinelPrimaryReconnectTimer, null);
+            oldTimer?.Dispose();
+        }
+
         /// <summary>
         /// Close all connections and release all resources associated with this object.
         /// </summary>

src/StackExchange.Redis/Interfaces/IConnectionMultiplexer.cs

@@ -20,7 +20,7 @@ internal interface IInternalConnectionMultiplexer : IConnectionMultiplexer
     /// <summary>
     /// Represents the abstract multiplexer API.
     /// </summary>
-    public interface IConnectionMultiplexer : IDisposable
+    public interface IConnectionMultiplexer : IDisposable, IAsyncDisposable
     {
         /// <summary>
         /// Gets the client-name that will be used on all new connections.

src/StackExchange.Redis/PublicAPI.Shipped.txt

@@ -308,6 +308,7 @@ StackExchange.Redis.ConnectionMultiplexer.ConfigureAsync(System.IO.TextWriter? l
 StackExchange.Redis.ConnectionMultiplexer.ConnectionFailed -> System.EventHandler<StackExchange.Redis.ConnectionFailedEventArgs!>?
 StackExchange.Redis.ConnectionMultiplexer.ConnectionRestored -> System.EventHandler<StackExchange.Redis.ConnectionFailedEventArgs!>?
 StackExchange.Redis.ConnectionMultiplexer.Dispose() -> void
+StackExchange.Redis.ConnectionMultiplexer.DisposeAsync() -> System.Threading.Tasks.ValueTask
 StackExchange.Redis.ConnectionMultiplexer.ErrorMessage -> System.EventHandler<StackExchange.Redis.RedisErrorEventArgs!>?
 StackExchange.Redis.ConnectionMultiplexer.ExportConfiguration(System.IO.Stream! destination, StackExchange.Redis.ExportOptions options = (StackExchange.Redis.ExportOptions)-1) -> void
 StackExchange.Redis.ConnectionMultiplexer.GetCounters() -> StackExchange.Redis.ServerCounters!

tests/StackExchange.Redis.Tests/SharedConnectionFixture.cs

@@ -128,6 +128,8 @@ public event EventHandler<HashSlotMovedEventArgs> HashSlotMoved
 
         public void Dispose() { } // DO NOT call _inner.Dispose();
 
+        public ValueTask DisposeAsync() => default; // DO NOT call _inner.DisposeAsync();
+
         public ServerCounters GetCounters() => _inner.GetCounters();
 
         public IDatabase GetDatabase(int db = -1, object? asyncState = null) => _inner.GetDatabase(db, asyncState);