string apiresource = Path.Combine(env.ContentRootPath, "apiResource/UpApp");
            FileHelper.CreateDirectory(apiresource);
            app.UseStaticFiles(new StaticFileOptions
            {

                //FileProvider = new PhysicalFileProvider(Directory.GetCurrentDirectory()),
                //设置不限制content-type 该设置可以下载所有类型的文件，但是不建议这么设置，因为不安全
                //ServeUnknownFileTypes = true 
                //下面设置可以下载apk和nupkg类型的文件
                RequestPath = "/apiResource/UpApp",
                FileProvider = new PhysicalFileProvider(apiresource),

                ContentTypeProvider = new FileExtensionContentTypeProvider(new Dictionary<string, string>
                {
                    { ".apk","application/vnd.android.package-archive"},
                    { ".nupkg","application/zip"}
                })
            });