Use cachix to publish binary cache

.github/workflows/cachix.yml

@@ -0,0 +1,17 @@
+name: "Build and push to cachix"
+on:
+  pull_request:
+  push:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2.3.4
+    - uses: cachix/install-nix-action@v12
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - uses: cachix/cachix-action@v8
+      with:
+        name: davegallant
+        authToken: '${{ secrets.CACHIX_API_KEY }}'
+    - run: nix-build | cachix push davegallant

flake.nix

@@ -24,7 +24,16 @@
               lib' = lib // import ./lib { inherit config lib; };
             };
 
-            nix.registry = { nixpkgs.flake = nixpkgs; };
+            nix = {
+              autoOptimiseStore = true;
+              binaryCaches = [ "https://davegallant.cachix.org" ];
+              binaryCachePublicKeys = [
+                "davegallant.cachix.org-1:SsUMqL4+tF2R3/G6X903E9laLlY1rES2QKFfePegF08="
+              ];
+              useSandbox = false;
+              registry = { nixpkgs.flake = nixpkgs; };
+              trustedUsers = [ "root" "dave" ];
+            };
 
             nixpkgs.overlays = [ (import ./overlays) ];
 

main/packages.nix

@@ -122,6 +122,7 @@
         kubernetes-helm
 
         # nix
+        cachix
         nix-index
         nixfmt
         nixpkgs-fmt