flake: now builds with nix build

flake.nix

@@ -25,6 +25,7 @@
         nixpkgs.lib.genAttrs supportedSystems (
           system:
           f {
+            inherit (nixpkgs) lib;
             pkgs = import nixpkgs { inherit system; };
           }
         );
@@ -32,10 +33,26 @@
     {
       # Schemas tell Nix about the structure of your flake's outputs
       schemas = flake-schemas.schemas;
-
+      packages = forEachSupportedSystem (
+        { pkgs, lib }:
+        {
+          default = pkgs.callPackage (
+            { buildGoModule }:
+            buildGoModule {
+              pname = "GoCalTui";
+              version = "0.0.1";
+              src = builtins.path {
+                name = "source";
+                path = ./.;
+              };
+              vendorHash = "sha256-SQHzChRwEx8VYJwXcZXTMDgILrhhRvGqrdQ1k3lFWgk=";
+            }
+          ) { };
+        }
+      );
       # Development environments
       devShells = forEachSupportedSystem (
-        { pkgs }:
+        { pkgs, ... }:
         {
           default = pkgs.mkShell {
             # Pinned packages available in the environment