获取系统时间
char time_buffer[20];
auto now = std::chrono::system_clock::now();
auto now_time = std::chrono::system_clock::to_time_t(now);
std::strftime(time_buffer, sizeof(time_buffer), "%Y-%m-%d %H:%M:%S", std::localtime(&now_time));
std::string current_time(time_buffer);