DependencyInjection.cs

using BareMinimumGoogleAuth.Data;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Authentication.Google;
using Microsoft.EntityFrameworkCore;

namespace BareMinimumGoogleAuth
{
    public static class DependencyInjection
    {
        public static IServiceCollection AddGoogleConfiguration(this IServiceCollection services, IConfiguration cfg)
        {
            var google = cfg.GetSection("Google");

            services.AddAuthentication(opt =>
            {
                opt.DefaultScheme = CookieAuthenticationDefaults.AuthenticationScheme;
                opt.DefaultChallengeScheme = GoogleDefaults.AuthenticationScheme;

            }).AddCookie()
             .AddGoogle(opt =>
             {
                 opt.ClientId = google["ClientId"]!;
                 opt.ClientSecret = google["ClientSecret"]!;
             });
            return services;
        }

        public static IServiceCollection AddDatabaseContext(this IServiceCollection services , IConfiguration cfg)
        {

            services.AddDbContext<GoogleContext>(opt =>
            {
                opt.UseNpgsql(cfg.GetConnectionString("DefaultConnection"));
            });


            return services;
        }
    }
}