I think the author just wan to said: choice Go is exactly a mistake.
No.
Go was a good choice. The project benefited from it, both from a hiring perspective and from a technical perspective. If I were in charge, I would make the exact same choice again.
Juju lives exactly in Go's sweet spot. A networked server worked on by more people than you can fit around your dining room table. Not every project would benefit from Go, but this one certainly did, IMO.