Effing package management! Build packages for multiple platforms (deb, rpm, etc) with great ease and sanity.

rcon is a lightweight resource virtualization tool for linux processes. This is one-binary.

Trusterd: High Performance HTTP/2 Web Server scripting with mruby

An effective ACME v2 client: Manage keys on the cloud (e.g. S3)

WebAuthn (U2F) helper for CLI operations (e.g. SSH Log in)

The guideline of your code

Translate MongoDB query to Arel AST for PostgreSQL JSON

eBPF query runner (Ruby DSL or something useful)