Startup.cs

using System;
using Autofac;
using Autofac.Extensions.DependencyInjection;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace my_online_shop
{
    public class Startup
    {
        private readonly string _connectionString;

        public Startup(IWebHostEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();

            Configuration = builder.Build();

            if (env.IsDevelopment())
            {
                _connectionString = Configuration.GetConnectionString("ConnectionStringLocal");
            }
            else
            {
                _connectionString = Environment.GetEnvironmentVariable("CONNECTION_STRING_HEROKU");
            }
        }


        public IConfiguration Configuration { get; }
        public static ILifetimeScope AutofacContainer { get; private set; }

        public void ConfigureContainer(ContainerBuilder builder)
        {
            var migrationAssemblyName = typeof(Startup).Assembly.FullName;

            builder.RegisterModule(new WebModule(_connectionString, migrationAssemblyName));
        }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddSession(options =>
            {
                options.IdleTimeout = TimeSpan.FromMinutes(30);
                options.Cookie.HttpOnly = true;
                options.Cookie.IsEssential = true;
            });

            services.AddControllersWithViews();
            services.AddRazorPages();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            AutofacContainer = app.ApplicationServices.GetAutofacRoot();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
                //app.UseDatabaseErrorPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/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.UseStaticFiles();
            app.UseRouting();
            app.UseSession();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
                endpoints.MapRazorPages();
            });
        }
    }
}