github.com/go-redis/cache初始化Codec

github.com/go-redis/cache包中 ring := redis.NewRing(&redis.RingOptions{ Addrs: map[string]string{ "server1": ":6379", "server2": ":6380", }, }) codec := &cache.Codec{ Redis: ring, Marshal: func(v interface{}) ([]byte, error) { return msgpack.Marshal(v) }, Unmarshal: func(b []byte, v interface{}) error { return msgpack.Unmarshal(b, v) }, } 其中ring的类型是*Ring，而Codec结构中的Redis类型是rediser，上面的初始化有点看不懂，请指教