Add garnix CI cache
diff --git a/flake.nix b/flake.nix
index ccf714a..fd128a1 100644
--- a/flake.nix
+++ b/flake.nix
@@ -37,6 +37,7 @@
             modules = [
               ./default/configuration.nix
               ./default/hardware-configuration.nix
+              ./modules/cache.nix
               ./modules/caddy.nix
               ./modules/clamav.nix
               ./modules/code-server.nix
diff --git a/modules/cache.nix b/modules/cache.nix
new file mode 100644
index 0000000..eee9d79
--- /dev/null
+++ b/modules/cache.nix
@@ -0,0 +1,8 @@
+{
+  nix.settings = {
+    substituters = [ "https://cache.garnix.io" ];
+    trusted-public-keys = [
+      "cache.garnix.io:CTFPyKSLcx5RMJKfLo5EEPUObbA78b0YQ2DTCJXqr9g="
+    ];
+  };
+}