ManagedWebSocket in System.Net.WebSockets.WebSocketProtocol is different from the implementation in System.Net.WebSockets for .NET 2.1. The former NuGet package is updated on May 5 as 4.5.0-rc1 (current), on the same day when Microsoft.NETCore.App package that includes the newest System.Net.WebSockets for .NET Core 2.1 was released as 2.1.0-rc1.

I had to dig into the source to find out that Microsoft.AspNetCore.WebSockets, also released on that day as 2.1.0-rc1-final, depends on System.Net.WebSockets.WebSocketProtocol and not on System.Net.WebSockets on this line. Unfortunately, that doesn't allow to enjoy the performance benefits from https://github.com/dotnet/corefx/issues/27445 when running ASPNETCore 2.1 apps.

Is this for a reason? How to use the latest low-allocations implementation currently in ASPNETCore 2.1 apps?