builtins.fetchTarball {url="https://github.com/NixOS/nixpkgs-channels/archive/b94c1c89f69563a9fc2ceee487b9bc19e5234d6a.tar.gz"; sha256="0gqk3dlkd03yj0vgp6hzaz8y62i5bccjnw657xij7cq3qypc28v5";}