Tailscalar here.
Go made prototyping our product easy. We have relatively rarely needed Go expertise on the team to make the product better, when we did it was for the exotic iOS environment (not normal iOS, the Network Extension).
It’s far from perfect (and I really should write an experience report about all the times Go has let us down!), but it gives us less trouble than Node and Swift do, for our relatively minor uses of those languages. I don’t think any other language would have been a better choice, even putting our expertise aside.
On the whole I would say you don’t need Go experts on your team to build products in the language.