The author states: "A few valiant attempts at bringing GC into systems programming -- Modula-3, Eiffel, Sather, D, Go -- have typically cut themselves off from too many tasks due to tracing GC overhead and runtime-system incompatibility, and still failed to provide a safe concurrency model."

Nim follows a different approach.

Details: http://nim-lang.org/docs/manual.html#threads

Benchmark (with Rust): https://github.com/costajob/app-servers