flake.nix

{
  description = "A small command tool line that loads enviroment variables from a file and executes a command.";
  # Nixpkgs / NixOS version to use.
  inputs.nixpkgs.url = "nixpkgs/nixos-22.05";

  outputs = { self, nixpkgs }:
    let

      # Generate a user-friendly version number.
      version = builtins.substring 0 8 self.lastModifiedDate;

      # System types to support.
      supportedSystems = [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin" ];

      # Helper function to generate an attrset '{ x86_64-linux = f "x86_64-linux"; ... }'.
      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;

      # Nixpkgs instantiated for supported system types.
      nixpkgsFor = forAllSystems (system: import nixpkgs { inherit system; });

    in
    {
      devShells = forAllSystems (system:
        let
          pkgs = nixpkgsFor.${system};
        in
          with pkgs;
        {
          default = mkShell {
            inputsFrom = builtins.attrValues self.packages.${system};
            buildInputs = [gopls gotools go-tools];
          };

        });

      packages = forAllSystems (system:
        let
          pkgs = nixpkgsFor.${system};
        in
          with pkgs;
        {
          default = buildGoModule {
            pname = "dotenv";
            inherit version;
            # In 'nix develop', we don't need a copy of the source tree
            # in the Nix store.
            src = ./.;

            vendorSha256 = "sha256-pQpattmS9VmO3ZIQUFn66az8GSmB4IvYhTTCFn6SUmo=";
          };

        });
    };
}