wxWidgets and <del>Swing</del>SWT are also platform-native. Now find me a single wxWidgets and SWT app that doesn't look slightly off on Linux and OS X.
Looking and feeling native involves so much more than just using native controls.
Looking and feeling native involves so much more than just using native controls.
wxWidgets and SWT are about as native at it can be in a cross platform GUI library. I don't see why you'd need a screenshot of the go library, it would look the same as a typical wxWidgets or SWT app, which is to say, it uses native controls, but might not be designed according to the "common" UI conventions of the platform.