> parallelism instead of concurrency/threads.
What do you mean? These seem synonymous to me.
> I thought Go has first class primitives to be able to do this?
TBH I'm only 1 week into learning Go myself (coming from Java/Scala/JS/etc). But it looks like the article used what Go offers. They used the atomic package which says, "provides low-level atomic memory primitives useful for implementing synchronization algorithms."