IdentityServer4 + ASP.NET Identity 无法删除cookie

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Logout(LogoutFormModel model)
{
    // build a model so the logged out page knows what to display
    var vm = await BuildLoggedOutViewModelAsync(model.LogoutId);

    if (User?.Identity.IsAuthenticated == true)
    {
        // delete local authentication cookie
        //await HttpContext.SignOutAsync(); // <-- replace this line
        await _signInManager.SignOutAsync(); // <-- with this one

        // raise the logout event
        await _events.RaiseAsync(new UserLogoutSuccessEvent(User.GetSubjectId(), User.GetDisplayName()));
    }

    return View("LoggedOut", vm);
}