Working through the Fly.io distributed systems challenge, in Rust.

The project is organized as a Cargo workspace. The maelstrom-* crates are libraries that provide the equivalent functionality as the Maelstrom Go package that is provided by Fly.io. The protocol crate especially is stand-alone and just provides the serializable/deserializable Rust types for Maelstrom messages. The node crate handles IO, while the gg-* crates are bin crates that implement the named challenge.