Make sure you have the righ C cross compiler for the target platform. Then you might encounter the usuall Wrong version of libc etc. So it's not enough to compile for goos=linux for example but also need to make sure that your C cross-compiler has the right version of libc for the target machine or Statically link the version you want, or deploy inside a container etc etc.

Pure Go? don't need anything else beside the Go compiler.

If you can avoid CGO, Avoid it.

When cross compiling pure Go you set an environment variable, build, and you have a binary ready to run, it is trivial.

When cross compiling with cgo you need a C cross compiling toolchain for the target platform installed with the right libc, etc. It is not impossible and that is how C/C++ is always cross compiled, but it is much more hassle than compiling pure Go.

I am in love with Zig (as you know), but feel the need to say: please be careful with blanket claims like this. purego is a pretty admirable approach to fixing cgo cross-compilation without Zig (though has its own drawbacks, like no static binary for example.)

Using Zig for Go cross-compilation, although quite great, isn't bulletproof. Finding the right CC/CXX incantation can be fairly tricky, the articles on this are not super up-to-date, and you need a copy of the macOS SDK[0] if you intend to cross-compile for macOS. You may also run into a few scary linker warnings and need to figure out the right Go build flags.

I definitely think Zig and Go can be best-friends, after all they share so many similar qualities and seem quite complementary to each-other. It's definitely possible to get Go<->Zig CGO cross compilation working (I did so for Sourcegraph); But Zig needs a little more love before it'll 'just work' as claimed for the Go use case, so best not to claim otherwise until then.

[0] https://github.com/ziglang/zig/issues/1349