I did something similar with `go bind`, a library used on both desktop and Android, they simply exchanged JSON, though not on millions of devices. However, today I have a nice cross-platform UI library with native controls, based on IUP, where cross-platform actually means everything, including iOS and Android (and even Haiku). So, you write an app in plain Go, just once, that's it. OK, you would not want the same layout on desktop and mobile, of course, but still the same app.

However, it is still a work in progress, and I would like to improve the mobile support. There are currently many Android-only or iOS-only attributes, but users would still miss some APIs. What are the most essential OS APIs one would need in the app? You can check the library here https://github.com/gen2brain/iup-go .