AccountController.cs

using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Mvc;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using APIViewWeb.Repositories;
using APIViewWeb.Models;

namespace APIViewWeb.Controllers
{
    [AllowAnonymous]
    public class AccountController : Controller
    {
        private readonly UserPreferenceCache _preferenceCache;
        public AccountController(UserPreferenceCache preferenceCache)
        {
            _preferenceCache = preferenceCache;
        }

        [HttpGet]
        public async Task<IActionResult> Login(string returnUrl = "/")
        {
            await HttpContext.SignOutAsync();
            if (!Url.IsLocalUrl(returnUrl))
            {
                returnUrl = "/";
            }
            return Challenge(new AuthenticationProperties() { RedirectUri = returnUrl }, "GitHub");
        }

        [HttpGet]
        public async Task<IActionResult> Logout()
        {
            await HttpContext.SignOutAsync();
            return RedirectToPage("/Login");
        }
    }
}