Update nix.yml (#9)

* Update nix.yml

.github/workflows/nix.yml

@@ -26,12 +26,13 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/[email protected]
-      - uses: cachix/install-nix-action@v8
-      - uses: cachix/cachix-action@v6
+      - uses: cachix/install-nix-action@v12
+      - uses: cachix/cachix-action@v8
         with:
           # Name of a cachix cache to push and pull/substitute
           name:  math-comp
+          extraPullNames: coq
           # Authentication token for Cachix, needed only for private cache access
-          signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
       # building fake mathcomp-fast target
       - run: nix-build --arg config '{coq = "${{ matrix.coq }}"; mathcomp = "${{ matrix.mc }}";}'