为了修复这个问题，需要修改中间件注册信息并确保配置文件正确。以下是修改后的示例代码：

using Autofac;
using Autofac.Extensions.DependencyInjection;
using log4net;
using log4net.Config;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System.Reflection;

namespace AutofacLog4NetMiddlewareExample
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
            //设置Log4Net配置文件
            XmlConfigurator.Configure(LogManager.GetRepository(Assembly.GetEntryAssembly()), new System.IO.FileInfo("log4net.config"));
        }

        public IConfiguration Configuration { get; }

        //Autofac注册容器
        public void ConfigureContainer(ContainerBuilder builder)
        {
            //将ILog接口注册为Log4NetLogger类型
            builder.RegisterType().As();

            //注册控制器以便进行属性注入
            builder.RegisterType().PropertiesAutowired();

            //注册中间件
            builder.RegisterType().PropertiesAutowired();
        }

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            //使用Log4Net作为ILogger的提供程序
            loggerFactory.AddLog4Net();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseHsts();
            }

            //注册中间件
            app.UseMiddleware();

            app.UseHttpsRedirection();
            app.UseMvc();
        }
    }

    //ILog接口实现
    public class Log4NetLogger : ILog
    {
        private readonly ILog _log;

        public Log4NetLogger()
        {
            _log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
        }

        public void Info(string message)
        {
            _log.Info(message);
        }
    }

    //中间