update mini get token

wechat/mini.go

@@ -63,20 +63,20 @@ func (mc *MiniClient) getToken() (token string, err error) {
 	key := keyMiniToken(mc.AppID)
 	var ct ClientToken
 	s := ``
-	s, err = cache.Get(key)
-	if err != nil {
-		return
-	}
-	err = json.Unmarshal([]byte(s), &ct)
-	if err != nil {
-		return
-	}
 	now := time.Now().Unix()
-	if mc.LastTokenTime > 0 {
-		if now-mc.LastTokenTime < TokenExpires {
-			token = mc.AccessToken
+	s, err = cache.Get(key)
+	if err == nil {
+		err = json.Unmarshal([]byte(s), &ct)
+		if err != nil {
 			return
 		}
+
+		if mc.LastTokenTime > 0 {
+			if now-mc.LastTokenTime < TokenExpires {
+				token = mc.AccessToken
+				return
+			}
+		}
 	}
 
 	uri := BaseURL + "/cgi-bin/token?"