call back function

func (u *Users) SqCallback(w http.ResponseWriter, r *http.Request) {
	log.Infof("\n****************\ncallback func begun\n****************\n")
	r.ParseForm()
	state := r.FormValue("state")
	cookie, err := r.Cookie("user_id")
	if err != nil {
		http.Error(w, err.Error(), http.StatusBadRequest)
		return
	} else if cookie == nil || cookie.Value != state {
		http.Error(w, "invalid state provided", http.StatusBadRequest)
		return
	}
	var hashKey = []byte(coCfg.HashKey)
	var blockKey = []byte(coCfg.BlockKey)
	var s2 = securecookie.New(hashKey, blockKey)
	value := make(map[string]string)
	if err = s2.Decode("user_id", cookie.Value, &value); err == nil {
		fmt.Println("heres the value", value["user_id"])
		fmt.Fprintf(w, "The value of userID is %q", value["user_id"])
	} else {
		fmt.Printf("\n\n*********ERROR************\n\n%#v\n\n*********************************************\n\n\n\n", err)
	}

	fmt.Printf("%#v", value)
	var dbUserID, _ = strconv.ParseUint(value["user_id"], 10, 32)
	var userID = uint(dbUserID)
	log.Infof("Customer dbID pulled from cookie state: %v\n\n***************", userID)

	code := r.FormValue("code")
	reqObj := map[string]string{
		"client_id":     sqOAuth.ClientID,
		"client_secret": sqOAuth.ClientSecret,
		"redirect_uri":  sqOAuth.RedirectURL,
		"code":          code,
	}

	jsonValue, _ := json.Marshal(reqObj)
	req, err := http.Post(sqOAuth.Endpoint.TokenURL, "application/json", bytes.NewBuffer(jsonValue))
	if err != nil {
		fmt.Printf("http request failed with error %s\n", err)
	} else {
		var m map[string]string
		_ = json.NewDecoder(req.Body).Decode(&m)
		req.Body.Close()
		expiresAt, _ := time.Parse(time.RFC3339, m["expires_at"])
		token := oauth2.Token{
			AccessToken: m["access_token"],
			TokenType:   m["token_type"],
			Expiry:      expiresAt,
		}

		userToken := model.OAuth{
			UserID:  userID,
			Service: "square",
			Token:   token,
		}

		u.os.Create(&userToken)
		if err != nil {
			panic(err)
		}
		log.Infof("Customer token saved in DB")

		http.Redirect(w, r, "/dashboard", http.StatusFound)

	}
}