Nix: move to devshell

flake.nix

@@ -1,22 +1,26 @@
 {
-  description = "Hugo website";
-  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+  description = "virtual environments";
+
+  inputs.devshell.url = "github:numtide/devshell";
   inputs.flake-utils.url = "github:numtide/flake-utils";
 
-  outputs =
-    { nixpkgs, flake-utils, ... }:
-    flake-utils.lib.eachDefaultSystem (
-      system:
-      let
-        pkgs = nixpkgs.legacyPackages.${system};
-      in
-      {
-        devShells.default = pkgs.mkShell {
-          packages = [
-            pkgs.go
-            pkgs.hugo
-          ];
+  inputs.flake-compat = {
+    url = "github:edolstra/flake-compat";
+    flake = false;
+  };
+
+  outputs = { self, flake-utils, devshell, nixpkgs, ... }:
+    flake-utils.lib.eachDefaultSystem (system: {
+      devShells.default =
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+
+            overlays = [ devshell.overlays.default ];
+          };
+        in
+        pkgs.devshell.mkShell {
+          imports = [ (pkgs.devshell.importTOML ./devshell.toml) ];
         };
-      }
-    );
+    });
 }