I didn’t claim it was new, I claimed it was different from typical coroutine implementations where you need to explicitly yield (all coroutines are cooperative

I didn’t claim it was new, I claimed it was different from typical coroutine implementations where you need to explicitly yield (all coroutines are cooperative multitasking by definition). I also claimed that this gives the usability properties of threads (you claimed that coroutines are somewhere between threads and callback hell WRT ease of use, which is true for traditional coroutines but not for goroutines. Another important distinction is that traditionally coroutines are not M:N, while goroutines are.