ASP.NET: Fixing the missing GetOwinContext method error by adding an Owin NuGet package

So you're working on an ASP.NET MVC web application, and you start working with authentication. You end up with the following C# compiler error:

'HttpContext' does not contain a definition for 'GetOwinContext' and
no extension method 'GetOwinContext' accepting a first argument of
type 'HttpContext' could be found (are you missing a using directive
or an assembly reference?)

How would you fix this error? The solution is luckily pretty simple: install the correct NuGet package. More specifically, you need the package called Microsoft.Owin.Host.SystemWeb. This package implements the missing GetOwinContext() method.

Problem solved!