FWIW I maintain an official implementation of the journal wire format in go now.
https://github.com/systemd/slog-journal so you can at least log to the journal now without CGO
But that's just the journal Wire format which is a lot simpler than the disk format.
I think a journal disk format parser in go would be a neat addition
I've got a pure Go journald file writer that works to some extent—it doesn't split, compress, etc, but it produces journal files that journalctl/sdjournal can read, concurrently. Only stress tested by running a bunch of parallel integration tests, will most likely not maintain it seriously, total newbie garbage, etc, but may be of interest to someone. I haven't really seen any other working journald file writers.
https://github.com/lessrest/swash/tree/main/pkg/journalfile