Equivalence is a symmetric relation. The article presents an example of a goroutine implementing an FSM. Even if you thought a single example constituted a proo

Equivalence is a symmetric relation. The article presents an example of a goroutine implementing an FSM. Even if you thought a single example constituted a proof, to show equivalence you'd also need to show how an arbitrary coroutine can be implemented using an FSM; and as others have observed, the ability to dynamically allocate memory distinguishes a coroutine from an FSM. That said, in practice, often we don't program with FSMs, we program with structures that are FSMs augmented with additional state such as counters and storage (collections/stacks/queues).