Go Mobile allows you to use the Go standard library and packages to build an SDK which integrates as a library by exposing C interfaces. With Android it creates the JNI stuff for you, iOS ObjectiveC bindings. As long as you avoid / be aware of any other C based dependencies it is pretty safe and maintainable.
Building an iOS framework still requires a mac as it needs to shell to xcodebuild but it does work pretty well.
With all of these tools you have to consider the Software Application Development lifecycle. What is the lifecycle of the application, are you prepared to completely re-write if the tooling disappears, can you suffer not being able to use the latest native framework while waiting for tools to update compatibility or are you prepared to pitch in and update the tooling yourself.
For me the main complexity with native apps is the UI, these APIs require specialist knowledge and can often wildly differ between platforms. React Native does a good job of abstraction and maybe this coupled to GoMobile is a dream partnership.