It doesn’t have to be rebuilt every time. The incremental parts are missing when compared to the Go compiler, but when coding a GUI app with Go you’re not modifying the C packages behind the scenes so they won’t need recompiled.
This means one rather slow compile to start and then it’s back to super fast!
Apple won't allow that. The only interpreted code is JS and must run on the built-in engine. Plus "dynamically added" code/content must first be approved by Apple or your app can be revoked.
Basically there is no shortcut here. Which is why the OP and others like Fyne (https://fyne.io) are taking the approach of write once, compile for anywhere.
It is fair what other commenters have said about Qt being larger and used more production. However it is a pain - from licensing and code/technology point of view.
If you enjoy Go and/or like maintainable GUI code then Fyne is basically designed for you. The team is ambitious and always developing more features, plus there is now commercial support behind the project at https://fynelabs.com.