Why is it ambiguous though? The second URL is nested

Are thy not accessed like

opts.URL == abc.com

and

opts.BarConnectionOptions.URL == xyz.com

what leads you think otherwise?

If there were no duplicate URL field, say they were called FooURL and BarcoURL, you could access them as `opts.FooURL` and `opts.BarcoURL`. They are both fields of `opts`, via embedding. It's just that FooURL is embedded directly, while BarcoURL is coming from two levels of embedding.