Haskell + GitHub Actions + Cachix

README.md

1. Put ci.yaml into .github/workflows/
2. Follow https://github.com/cachix/cachix-action#usage to setup Cachix and benefit from quick CI build times.

ci.yaml

name: "CI"
on:
  pull_request:
  push:
jobs:
  tests:
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2.3.1
    - uses: cachix/install-nix-action@v10
      with:
        skip_adding_nixpkgs_channel: true
    - uses: cachix/cachix-action@v6
      with:
        name: mycache
        signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
    - run: cachix use iohk
    - run: nix-build -A mypackage.components.all

default.nix

{ haskellNix ? import (builtins.fetchTarball "https://github.com/input-output-hk/haskell.nix/archive/dc7acfeb7628032d5109747a8b330d58817b953f.tar.gz") {}
, nixpkgsSrc ? haskellNix.sources.nixpkgs-2003
, nixpkgsArgs ? haskellNix.nixpkgsArgs
, pkgs ? import nixpkgsSrc nixpkgsArgs
}: 

pkgs.haskell-nix.project {
  src = pkgs.haskell-nix.haskellLib.cleanGit {
    name = "haskell-nix-project";
    src = ./.;
  };
}

This is outdated because the iohk cachix cache is no longer updated.

https://input-output-hk.github.io/haskell.nix/tutorials/getting-started/#setting-up-the-binary-cache

Yeah, you need to use hydra.iohk.io