It's the web. It runs HTML, CSS and JS.Why? Is there some first-principles thing here? What if Flash was open sourced, massively cleaned up, changed to be search friendly, and ended up with well curated app marketplaces and code signing? The language Flash used had a shared heritage with JS, and actually did a better job of providing "just works" write once, run everywhere.
Many Smalltalk variants had a practically bulletproof write once, run everywhere record of performance. What if properly code signed and sandboxed Smalltalk plugins had won? That could well have resulted in a more open web than what we ended up with.
Wanting to code your web app in anything else is... I don't know... petulant?
Why?
There are currently exactly zero Front End Developers who write usable web front ends in Go.
If the developer experience becomes a lot more like developing against a desktop UI framework, there are a ton of experienced older developers who could quickly jump in. It's not rocket science. Actually, in many ways, desktop development is easier than the web front end.
For that matter, why not build something which is 1-to-1 isomorphic with React? (EDIT: I see now, that's already sort of the direction they're going for!)
I'm not sure moving to a Go front end is wise for another few years.
Which I would interpret as a sign that it's the right time to jump in to be a pioneer!