一：什么是协程(Coroutines)：

      协程是轻量级线程，可以暂停和恢复执行，协程拥有自己的暂停点状态，协程暂停时，将当前状态保存起来，在恢复执行时会恢复之前保存的状态。

二：例子：

#include <coroutine>
#include <iostream>void doTheWork() {std::cout << "Processing shared data." << std::endl;
}
template<typename T>
struct Generator {struct promise_type;using handle_type = std::coroutine_handle<promise_type>;Generator(handle_type h) : coro(h) {} // (3) //创建生成器handle_type coro;~Generator() {if (coro) coro.destroy();}Generator(const Generator&) = delete;Generator& operator = (const Generator&) = delete;Generator(Generator&& oth) noexcept : coro(oth.coro) {oth.coro = nullptr;}Generator& operator = (Generator&& oth) noexcept {coro = oth.coro;oth.coro = nullptr;return *this;}T getValue() {re