Add flake for devshell

.envrc

@@ -0,0 +1 @@
+use flake

.gitignore

@@ -1,3 +1,4 @@
 *.exe
 test_data/
 tmp/
+.direnv/

flake.lock

@@ -0,0 +1,60 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1751984180,
+        "narHash": "sha256-LwWRsENAZJKUdD3SpLluwDmdXY9F45ZEgCb0X+xgOL0=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "9807714d6944a957c2e036f84b0ff8caf9930bc0",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "ref": "nixos-unstable",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs",
+        "utils": "utils"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,25 @@
+{
+	inputs = {
+		utils.url = "github:numtide/flake-utils";
+		nixpkgs.url = "nixpkgs/nixos-unstable";
+	};
+
+	outputs = { self, nixpkgs, utils }:
+		utils.lib.eachDefaultSystem (system:
+			let
+				pkgs = nixpkgs.legacyPackages."${system}";
+			in rec {
+				devShell = pkgs.mkShell {
+					shellHook = ''
+						export SHELL=${pkgs.fish}/bin/fish
+					'';
+					nativeBuildInputs = with pkgs; [
+						go_1_24
+						gopls
+						golangci-lint
+						golangci-lint-langserver
+					];
+				};
+			}
+		);
+}