Add file server from relative path, named wwwroot.

self-host-configuration-fileserve

class Startup {
  public void Configuration(IAppBuilder app){            
    if (!Directory.Exists("wwwroot")) Directory.CreateDirectory("wwwroot");

            var physicalFileSystem = new PhysicalFileSystem("./wwwroot");

            // file server options
            var options = new FileServerOptions
            {
                EnableDefaultFiles = true,
                FileSystem = physicalFileSystem, // register file system
                EnableDirectoryBrowsing = false
            };

            options.StaticFileOptions.FileSystem = physicalFileSystem;
            options.StaticFileOptions.ServeUnknownFileTypes = true;
            options.DefaultFilesOptions.DefaultFileNames = new[] { "index.html" };
            //app.Use<DefaultFileRewriterMiddleware>(physicalFileSystem);  // middleware to direct non-existing file URLs to index.html
            app.UseFileServer(options);
  }
}