fix nil bug

middleware/auth/session_redis.go

 }
 
 func NewRedisSessionStore(address string, password string) *RedisSessionStore {
-	session := &RedisSessionStore{}
+	session := &RedisSessionStore{once:&sync.Once{}}
 	session.once.Do(func() {
 		session.client = redis.NewClient(&redis.Options{
 			Addr:     address,