Project structure refactor:

- Change package name general_server to gateway
- Changing the structure of directories and packages
- Adding vendor to the project

vendor/github.com/go-viper/mapstructure/v2/flake.nix

@@ -0,0 +1,46 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    devenv.url = "github:cachix/devenv";
+  };
+
+  outputs =
+    inputs@{ flake-parts, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } {
+      imports = [
+        inputs.devenv.flakeModule
+      ];
+
+      systems = [
+        "x86_64-linux"
+        "x86_64-darwin"
+        "aarch64-darwin"
+      ];
+
+      perSystem =
+        { pkgs, ... }:
+        rec {
+          devenv.shells = {
+            default = {
+              languages = {
+                go.enable = true;
+              };
+
+              pre-commit.hooks = {
+                nixpkgs-fmt.enable = true;
+              };
+
+              packages = with pkgs; [
+                golangci-lint
+              ];
+
+              # https://github.com/cachix/devenv/issues/528#issuecomment-1556108767
+              containers = pkgs.lib.mkForce { };
+            };
+
+            ci = devenv.shells.default;
+          };
+        };
+    };
+}