I wanted to generate a checksum of an entire directory and its contents. For this, there's two approaches, one hashes the files in a directory, the other hashes a zip while ignoring non-deterministic information like file date.
Extra metadata isn't necessarily meaningful for file contents and should probably be ignored.
The Parallel digestion example from the https://blog.golang.org/pipelines, starting from the Digesting a tree section, gave me this code, but I intend to modify it to suit my needs.
Specifically, the parallel version: https://blog.golang.org/pipelines/parallel.go
For go mod Russ Cox wrote dirhash.