如何编写返回impl Future的函数指针签名？

typedef impl Future (*MyFutureFn)();

typedef boost::asio::awaitable<void> (*MyFutureFn)();

#include <iostream>
#include <boost/asio.hpp>

typedef boost::asio::awaitable<void> (*MyFutureFn)();

boost::asio::awaitable<void> myFuture()
{
    // 异步操作的实现
    co_return;
}

int main()
{
    MyFutureFn fn = &myFuture;
    // 调用函数指针
    boost::asio::io_context ioContext;
    boost::asio::co_spawn(ioContext, fn(), [](const boost::system::error_code& error) {
        if (error)
        {
            std::cout << "Error: " << error.message() << std::endl;
        }
    });
    ioContext.run();

    return 0;
}