make environment shutdown asynchronous
diff --git a/src/csharp/Grpc.Core/Channel.cs b/src/csharp/Grpc.Core/Channel.cs
index 9cee752..b58a6a7 100644
--- a/src/csharp/Grpc.Core/Channel.cs
+++ b/src/csharp/Grpc.Core/Channel.cs
@@ -220,7 +220,7 @@
 
             handle.Dispose();
 
-            await Task.Run(() => GrpcEnvironment.Release()).ConfigureAwait(false);
+            await GrpcEnvironment.ReleaseAsync().ConfigureAwait(false);
         }
 
         internal ChannelSafeHandle Handle