Guix

Fibers is a Guile library that implements a a lightweight concurrency facility, inspired by systems like Concurrent ML, Go, and Erlang. A fiber is like a "goroutine" from the Go language: a lightweight thread-like abstraction. Systems built with Fibers can scale up to millions of concurrent fibers, tens of thousands of concurrent socket connections, and many parallel cores. The Fibers library also provides Concurrent ML-like channels for communication between fibers.

Note that Fibers makes use of some Guile 2.1/2.2-specific features and is not available for Guile 2.0.