True, but I think that the "mainstream-ness" of Go (debatable as it is) was of secondary importance to the article, which didn't even mention that there are oth

True, but I think that the "mainstream-ness" of Go (debatable as it is) was of secondary importance to the article, which didn't even mention that there are other languages out there which solve the concurrency problem in other/better ways. Whether or not a language is mainstream is more or less a matter of opinion, in any case. Certainly Haskell, Rust or Erlang (to name a few) are probably less widely used than Go, but none of them are obscure, so to not mention them at all suggests that the author is either being disingenuous, is not aware of those languages' capabilities, or simply forgot.