Definitely not a minor feedback, there's no reason to write go in a .js file. Vite/rollup are perfectly able to "load" certain file types and parse them however you like.
Modern tools often make this tradeoff, like Astro, and none of the tools authors are claiming you need to use the tool.
Yes, the pattern can be abused, but dogmatic rules against mixing languages may also entail downsides.
To be clear I'm fine with importing .go from JS, it's the "go in file.js" thing I don't like.