Rust does not require a runtime / garbage collector and offers a programming model that interacts very precisely with external threading requirements. It supports being called from the native platform ABI without initialization, and it supports writing libraries to match an existing, native ("C") ABI and function as a drop-in replacement. Go does not do these things.

The suggestion to use Rust here is because this is specifically a thing Rust was designed to do, not because it has a huge following. Go is a great language, but it is designed for different things (and has a following of people who want it to do those different things). If those two languages are the two choices for replacing a codec that functions as a library, there is an objectively correct answer.