C++20 Coroutines

Is there a way to use this library with C++20 coroutines?
Would be nice to just write

```cpp 
    auto [res, ec] = co_await api.account_info();
    if(!ec) {
        std::cout << "account info: " << res << std::endl;
    }
```

asio already supports this with `asio::awaitable<...>` so would be awesome if this lib supports this modern C++ style