Native DNS lookups is possible in Go on macOS. But it seems the road to get there was not exactly smooth.

It's not difficult, and it was done like that for some time, but the macOS system call interface is not guaranteed to be stable (more like guaranteed to be unstable), so the correct thing on macOS is to go through libc (libSystem), which Go now does since 1.12.

Not exactly rocket science perhaps, but AFAICT there was some long-running tickets related to DNS lookups on macOS.

For DNS specifically, this landed in Go 1.20: here is the change set [1].

A different change [2] had a similar effect of using the system facilities for certificate validation in 1.18.

In general, using the custom stuff “works” (until it doesn’t!) but results in janky programs that don’t behave with respect to split tunnel DNS and so forth - very common with cross compiled programs until recently.

[1]: https://go-review.googlesource.com/c/go/+/446178

[2]: https://go-review.googlesource.com/c/go/+/353132

Is dns lookup provided by the kernel on macOS? I'm pretty sure this would all be done in userspace anyway.

There is no "native" way to do this unless you consider libc (or libsystem) "native". There is no kernel interface to do dnd lookups just standard userspace tooling.