chore: clean flake

default.nix

@@ -1,7 +1,8 @@
-{ system ? builtins.currentSystem
-, nixpkgs ? import <nixpkgs> { inherit system; }
-}:
 {
+  system ? builtins.currentSystem,
+  nixpkgs ? import <nixpkgs> { inherit system; },
+}:
+rec {
   nar-serve = nixpkgs.buildGoModule {
     pname = "nar-serve";
     version = "latest";
@@ -10,5 +11,7 @@
     doCheck = false;
   };
 
+  default = nar-serve;
+
   devShell = import ./shell.nix { inherit nixpkgs; };
 }

flake.nix

@@ -1,21 +1,29 @@
 {
   description = "NAR serve";
 
-  inputs.flake-utils.url = "github:numtide/flake-utils";
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs?ref=nixos-unstable";
+    systems.url = "github:nix-systems/default";
+  };
 
-  outputs = { self, nixpkgs, flake-utils }:
+  outputs =
     {
-      overlay = import ./overlay.nix;
-    }
-    //
-    flake-utils.lib.eachDefaultSystem (system:
-      let
-        pkgs = nixpkgs.legacyPackages.${system};
-      in
-      rec {
-        packages = import ./. { nixpkgs = pkgs; };
-        defaultPackage = packages.nar-serve;
-        devShell = packages.devShell;
-      }
-    );
+      self,
+      nixpkgs,
+      systems,
+    }:
+    let
+      eachSystem = f: nixpkgs.lib.genAttrs (import systems) (system: f nixpkgs.legacyPackages.${system});
+    in
+    {
+      overlays.default = import ./overlay.nix;
+
+      packages = eachSystem (pkgs: import ./. { nixpkgs = pkgs; });
+
+      formatter = eachSystem (pkgs: pkgs.nixfmt-rfc-style);
+
+      devShells = eachSystem (pkgs: {
+        default = self.packages.${pkgs.system}.devShell;
+      });
+    };
 }

overlay.nix

@@ -1,3 +1 @@
-final: prev: {
-  nar-serve = import ./. { nixpkgs = final; };
-}
+final: prev: { nar-serve = import ./. { nixpkgs = final; }; }

shell.nix

@@ -1,5 +1,6 @@
-{ system ? builtins.currentSystem
-, nixpkgs ? import <nixpkgs> { inherit system; }
+{
+  system ? builtins.currentSystem,
+  nixpkgs ? import <nixpkgs> { inherit system; },
 }:
 nixpkgs.mkShell {
   buildInputs = with nixpkgs; [