在C++ std中，如何在运行时选择时序的持续时间

#include <iostream>
#include <chrono>

int main() {
    int durationChoice;
    std::cout << "请选择持续时间单位：\n";
    std::cout << "1. 秒\n";
    std::cout << "2. 毫秒\n";
    std::cout << "3. 微秒\n";
    std::cout << "4. 纳秒\n";
    std::cin >> durationChoice;

    std::chrono::duration<long long> duration;

    switch (durationChoice) {
        case 1:
            duration = std::chrono::seconds(1);
            break;
        case 2:
            duration = std::chrono::milliseconds(1);
            break;
        case 3:
            duration = std::chrono::microseconds(1);
            break;
        case 4:
            duration = std::chrono::nanoseconds(1);
            break;
        default:
            std::cout << "无效的选择\n";
            return 0;
    }

    std::cout << "持续时间为：" << duration.count() << "个时间单位\n";

    return 0;
}