/// <summary>
 /// Use RedisSession. After enabled, you can take RedisSession from environment.AsRedisSession().
 /// </summary>
 public static IAppBuilder UseRedisSession(this IAppBuilder app, RedisSessionOptions options)
 {
     return app.Use(typeof(RedisSessionMiddleware), options);
 }
 public RedisSessionMiddleware(AppFunc next, RedisSessionOptions options)
 {
     this.next = next;
     this.options = options;
 }