CPP20 - yszheda/wiki GitHub Wiki
https://github.com/Cpp-Club/Cxx_HOPL4_zh
coroutine
- https://en.wikipedia.org/wiki/Coroutine
- https://stackoverflow.com/questions/43503656/what-are-coroutines-in-c20
https://github.com/Cpp-Club/Cxx_HOPL4_zh
std::identity