Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication.OAuth;
using Microsoft.AspNetCore.Http;
using Microsoft.EntityFrameworkCore;
using DMPackageManager.Website.Database;
using Microsoft.AspNetCore.Identity;
using Microsoft.Extensions.Identity.Core;
using Microsoft.AspNetCore.Authentication.Cookies;
using AspNet.Security.OAuth.GitHub;
using Microsoft.AspNetCore.Authentication;
using System.Security.Claims;

namespace DMPackageManager.Website {
    public class Startup {
        public Startup(IConfiguration configuration) {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services) {
            services.AddDbContext<DatabaseContext>(options => options.UseMySql(Configuration["Database:ConnectionString"], ServerVersion.AutoDetect(Configuration["Database:ConnectionString"])));
            services.AddAuthentication(options => {
                options.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                options.DefaultChallengeScheme = GitHubAuthenticationDefaults.AuthenticationScheme;
            }).AddCookie().AddGitHub(options => {
                options.ClientId = Configuration["GitHub:client_id"];
                options.ClientSecret = Configuration["GitHub:client_secret"];
                options.CallbackPath = "/oauth_callback";
            });
            services.AddControllersWithViews();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, DatabaseContext dbc) {
            if (env.IsDevelopment()) {
                app.UseDeveloperExceptionPage();
            } else {
                app.UseExceptionHandler("/error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthentication();
            app.UseAuthorization();

            dbc.Database.EnsureCreated();

            app.UseEndpoints(endpoints => {
                endpoints.MapDefaultControllerRoute();
            });
        }
    }
}