fix: 当回复消息类型为markdown时,at功能不生效 (#272)

Co-authored-by: baomi.wbm <baomi.wbm@dtwave-inc.com>

pkg/dingbot/dingbot.go

@@ -97,6 +97,9 @@ func (r ReceiveMsg) ReplyToDingtalk(msgType, msg string) (statuscode int, err er
 	case string(TEXT):
 		msgtmp = &TextMessage{Text: &Text{Content: msg}, MsgType: TEXT, At: &At{AtUserIds: []string{atUser}}}
 	case string(MARKDOWN):
+		if atUser != "" {
+			msg = fmt.Sprintf("%s\n\n@%s", msg, atUser)
+		}
 		msgtmp = &MarkDownMessage{MsgType: MARKDOWN, At: &At{AtUserIds: []string{atUser}}, MarkDown: &MarkDown{Title: "Markdown Type", Text: msg}}
 	default:
 		msgtmp = &TextMessage{Text: &Text{Content: msg}, MsgType: TEXT, At: &At{AtUserIds: []string{atUser}}}