If I was going to try to make something "similar to Wordpress" with Go I would replace plugins with optional packages triggered by build flags (or possibly a light codegen step), not an actual dynamic plugin system. The Wordpress model is solved with plugins in PHP (for reasons that were to some degree bad even at the time), but it's not actually "I want to inject some external code into this existing process environment", it's "I want a bespoke N of M features because some Ms are mutually exclusive or have overhead I can't afford".

If you have a language that has a module ecosystem, compiles fast, and generates a single binary, take advantage of that; don't try to reimplement fragile dynamic linking.