Beyond linking it is also a problem with ABI compatibility of object layouts, etc. It is so much simpler with more dynamic languages.
I wish https://pkg.go.dev/plugin was clearly documented as not being a viable 3rd party plugin solution.
(There are also higher-level ABIs like COM, but they are usually reducible to the C ABI in practice - e.g. COM can be described entirely in terms of struct and function pointers.)