public class AuthorisationAttribute : TypeFilterAttribute
{
    public AuthorisationAttribute() : base(typeof(AuthorisationFilter))
    {
        Arguments = new object[] { new Claim(ClaimTypes.UserData, "will be my user data") };
    }
}
 public class AuthorisationFilter : IAuthorizationFilter
{
    readonly HttpContext _httpContext;
    public AuthorisationFilter(HttpContext httpContext)
    {
        _httpContext = httpContext;
    }

    public void OnAuthorization(AuthorizationFilterContext context)
    {
        var authorisationCookie = context.HttpContext.Request.Headers.Where(t => t.Key == "auth").FirstOrDefault();

        var temp = new JwtSecurityTokenHandler();
        var unencryptedToken = temp.ReadToken(authorisationCookie.Value) as JwtSecurityToken;

        var session = _httpContext.Session;
        //MORE TO DO HERE YET! Just want to test getting called when expected.
        return;
    }
}

public class HomeController : Controller
{
    [Authorisation(),HttpGet]
    public IActionResult Index()
    {
          return View("~/Views/Home/Index.cshtml");
    }
}

services.AddHttpContextAccessor();

public AuthorisationFilter(IHttpContextAccessor httpContextAccessor)
{
    _httpContextAccessor = httpContextAccessor;
}

context.HttpContext