Simple Meyers singleton example C++17

meyers_singleton.cpp

#include <string>
#include <iostream>
#include <chrono>
#include <thread>
#include <format> // Requires C++20

using system_clock = std::chrono::system_clock;
using namespace std::chrono_literals;

const std::string& get_static_message() {
    // Will be constructed exactly once
    static const std::string msg = std::to_string(system_clock::now().time_since_epoch().count());
    return msg;
}

int main() {
    std::cout << std::format("First invocation: {}\n", get_static_message());
    std::this_thread::sleep_for(5s);
    std::cout << std::format("Second invocation: {}\n", get_static_message());
    // Possible output, note that the result from the get_static_message is the same!:
    // First invocation: 16614610160060892
    // Second invocation: 16614610160060892
}