Note that neither CockroachDB or TiDB use Golang for their actual storage engine, which is in both cases written in C (RocksDB). They do use Golang for SQL parsing though, which is what this post was mostly about.
VictoriaMetrics [1] is written entirely in Go. By default it uses canonical zstd library for compression (the library is written in C), but it supports pure Go mode when built with `make victoria-metrics-pure`. In this mode it uses zstd implementation written in Go [2].
There's also DGraph based on Badger as a storage engine which is an all-go stack.
And badger does compare favorably to rocksdb under certain workloads.