{
  source,
  pkgs ? (
    let
      inherit (builtins) fetchTree fromJSON readFile;
      inherit ((fromJSON (readFile ./flake.lock)).nodes) nixpkgs gomod2nix;
    in
      import (fetchTree nixpkgs.locked) {
        overlays = [
          (import "${fetchTree gomod2nix.locked}/overlay.nix")
        ];
      }
  ),
  mkGoEnv ? pkgs.mkGoEnv,
  gomod2nix ? pkgs.gomod2nix,
}: let
  update_gomod2nix = pkgs.writeShellScriptBin "update_gomod2nix" ''
    ${gomod2nix}/bin/gomod2nix --dir ${source} --outdir ./
  '';
in
  pkgs.mkShell {
    packages = [
      gomod2nix
      update_gomod2nix
    ];
  }