ASP.NET Core 1.0 中使用Log日志

public Startup(IApplicationEnvironment appEnv)
        {
            IConfigurationBuilder builder = new ConfigurationBuilder()
                .SetBasePath(appEnv.ApplicationBasePath)
                .AddJsonFile("config.json", false);
            Configuration = builder.Build();

            var logFilePath = Path.Combine(appEnv.ApplicationBasePath,"logs/log.txt");
            Log.Logger = new LoggerConfiguration()
                    .MinimumLevel.Debug()
                    .WriteTo.TextWriter(new StreamWriter(
                        new FileStream(logFilePath, FileMode.OpenOrCreate)))
                    .CreateLogger();    
        }

        public IConfiguration Configuration { get; set; }

        public void Configure(IApplicationBuilder app, ILoggerFactory loggerFactory)
        {
            loggerFactory
                .AddSerilog()
                .AddConsole();

            app.UseDeveloperExceptionPage();
            app.UseMvcWithDefaultRoute();            
            app.UseStaticFiles();            
            app.UseRuntimeInfoPage();
        }

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