pkg.go.dev
In short: Go Packages (pkg.go.dev) accepts go module documentation page. It is free to submit, takes a moderate amount of preparation, and scores 84/100 on our impact ranking (high impact).
Tag and publish a public Go module with module docs and repository metadata so pkg.go.dev indexes it.
Use a valid module path and semantic-version tag; the module becomes discoverable after the proxy fetches it.
Priority is high, which sets the band. It is free and moderate to complete, which adjusts it within that band. The score ranks your queue — it is not a measure of domain authority.