/// <summary>
/// 收到 "本月已發送訊息數" 後會回覆的文字
/// </summary>
/// <returns></returns>
private async Task <string> GetNumberOfMessagesSentThisMonthTips()
{
string result = "";
NumberOfMessagesSentThisMonthResponseModel responseModel = new NumberOfMessagesSentThisMonthResponseModel();
responseModel = await _lineClient.GetNumberOfMessagesSentThisMonthAsync();
result = $"本月已發送訊息的數量為 : {responseModel.totalUsage}";
return(result);
}