Given that even on Linux DNS resolution in Go can be quite... interesting without CGO being enabled, honestly it's hardly surprising that on iOS it would also be quite challenging.

I imagine that one more interesting thing to consider is that on iOS you can't fork() or spawn sub-processes, so your Go mobile app is indeed running simultaneously as a Go binary and the UI, and there probably can exist countless interactions between the two being unaware of each other that might cause issues

Who enables CGO just for DNS resolution? That is not a thing for a long time, you just reminded me of that. Sure, if you have some complex config instead of a simple default, you would want to use libc and getaddrinfo, that is on you. What other issues are there? Go simple uses the network protocol for DNS, and it reads just resolve.conf; it does not care about LDAP or NSS or whatever there is.