Add using

Marusyk · Marusyk · commit 500ab605d3ac · 2019-11-24T00:35:58.000+02:00
diff --git a/src/SignalR/server/Core/src/HubClientsExtensions.cs b/src/SignalR/server/Core/src/HubClientsExtensions.cs
@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System.Collections.Generic;
+using System.Linq;
 
 namespace Microsoft.AspNetCore.SignalR
 {

Original file line number	Diff line number	Diff line change
`@@ -2,6 +2,7 @@`
`2`	`2`	`// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.`
`3`	`3`
`4`	`4`	`using System.Collections.Generic;`
	`5`	`+using System.Linq;`
`5`	`6`
`6`	`7`	`namespace Microsoft.AspNetCore.SignalR`
`7`	`8`	`{`