netcore 中间件记录日志

public class Logger
    {
        private static ILog logger;
       static Logger()
        {
            if (logger == null)
            {
                var repository = LogManager.CreateRepository("NETCoreRepository");
                //log4net从log4net.config文件中读取配置信息
                XmlConfigurator.Configure(repository, new FileInfo("log4net.config"));
                logger = LogManager.GetLogger(repository.Name, "Logger");
            }
        }
        private RequestDelegate _nextDelegate;
        public Logger(RequestDelegate nextDelegate)
        {
            _nextDelegate = nextDelegate;
        }
        public async Task Invoke(HttpContext httpContext)
        {
            logger.Info("start:" + DateTime.Now.ToString());
            await _nextDelegate.Invoke(httpContext);
            logger.Info("end:" + DateTime.Now.ToString());
        }
        public static void Info(string message, Exception exception = null)
        {
            if (exception == null)
                logger.Info(message);
            else
                logger.Info(message, exception);
        }
        public static void Warn(string message, Exception exception = null)
        {
            if (exception == null)
                logger.Warn(message);
            else
                logger.Warn(message, exception);
        }
        public static void Error(string message, Exception exception = null)
        {
            if (exception == null)
                logger.Error(message);
            else
                logger.Error(message, exception);
        }
    }

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                // 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.UseMiddleware<Logger>();
            app.UseMvc();
            
        }