indeed, wal-g actually started as a port of wal-e which was Python: https://www.citusdata.com/blog/2017/08/18/introducing-wal-g-...
wal-g was a much larger improvement over wal-e. we're optimizing the margins here
++ We’re big Go fans, most of PeerDB is written in Go: https://github.com/PeerDB-io/peerdb
The importance of optimizing (resource) margins and having predictable memory usage increases significantly in the DBaaS/Postgres world, where your process coexists and competes with other critical workloads.
Also, WAL-RUS isn’t rocket science. Postgres already exposes a bunch native constructs for WAL archival, making development fairly straightforward even in Rust.
TL;DR: when to choose Rust or Go really depends on the workload and what you are going after.
I'd like to use the one getting the most community support. So too soon to wait for Rust vs Go. Although on paper, Rust is better.