以下錯誤：./main.go:13: c.Set undefined (type redis.Conn has no field or method Set)./main.go:19: invalid receiver type *redis.Conn (redis.Conn is an interface type)./main.go:20: red.Send undefined (type *redis.Conn has no field or method Send)是從這個代碼產生的：package mainimport (    "encoding/json"    "github.com/garyburd/redigo/redis"    "github.com/gorilla/mux"    "log"    "net/http"    )func setHandler(res http.ResponseWriter, req *http.Request) {    c := connectRedis()    c.Set("foo", "bar")    data, _ := json.Marshal("{'order':1, 'weight': 100, 'reps': 5, 'rest': 1}")    res.Header().Set("Content-Type", "application/json; charset=utf-8")    res.Write(data)}func (red *redis.Conn) Set(key string, value string) error {    if _, err := red.Send("set", key, value); err != nil {        return err    }}func connectRedis() redis.Conn {    c, err := redis.Dial("tcp", ":6379")    if err != nil {            // handle error    }    defer c.Close()    return c}func main() {    r := mux.NewRouter()    r.HandleFunc("/sets.json", setHandler)    http.Handle("/", r)    err := http.ListenAndServe(":7000", nil)    if err != nil {        log.Fatal("ListenAndServe: ", err)    }}當我有一個接口時，如何注冊一個方法？