feat: add nix dev flake

flake.nix

@@ -0,0 +1,38 @@
+{
+  description = "A Nix-flake-based Go 1.22 development environment";
+
+  inputs.nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/0.1.*.tar.gz";
+
+  outputs = { self, nixpkgs }:
+    let
+      goVersion = 24; # Change this to update the whole stack
+
+      supportedSystems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forEachSupportedSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ self.overlays.default ];
+        };
+      });
+    in
+    {
+      overlays.default = final: prev: {
+        go = final."go_1_${toString goVersion}";
+      };
+
+      devShells = forEachSupportedSystem ({ pkgs }: {
+        default = pkgs.mkShell {
+          packages = with pkgs; [
+            # go (version is specified by overlay)
+            go
+
+            # goimports, godoc, etc.
+            gotools
+
+            # https://github.com/golangci/golangci-lint
+            golangci-lint
+          ];
+        };
+      });
+    };
+}