app.UseStaticFiles();//默認靜態文件目錄是wwwroot

StaticFiles(app, env);

        /// <summary>
        /// 靜態文件
        /// </summary>
        /// <param name="app"></param>
        /// <param name="env"></param>
        /// <returns></returns>
        private void StaticFiles(IApplicationBuilder app, IWebHostEnvironment env)
        {
            //靜態文件重載
            app.UseStaticFiles(new StaticFileOptions
            {
                FileProvider = new PhysicalFileProvider(Path.Combine(env.ContentRootPath, "Upload")), //將目錄切換到靜態文件所在目錄
                RequestPath =new PathString("/fileupload"), //虛擬路徑用來訪問靜態文件
                OnPrepareResponse = ctx =>
                {
                    const int cacheControl = 60;//設置緩存靜態文件的時間
                    var headers = ctx.Context.Response.GetTypedHeaders();
                    headers.CacheControl = new CacheControlHeaderValue
                    {
                        MaxAge = TimeSpan.FromSeconds(cacheControl)
                    };
                }
            });
        }