Liteloader Installation

You need to provide the direct url to the liteloader version you want to use. Go here, select your minecraft version and select the build type. Then hover over the jar installer link, right click, and copy link.

programs.minecraft = {
  enable = true;
  instances = {
    "your-liteloader-instance-name" = {
      minecraft.version = "1.12.2";
      liteloader.url = "http://jenkins.liteloader.com/job/LiteLoaderInstaller%201.12.2/lastSuccessfulBuild/artifact/build/libs/liteloader-installer-1.12.2-00-SNAPSHOT.jar";
      liteloader.hash = "sha256-AfxOgCWliIAMBlMTOMC3gdSShuRB5E6yYYIw0fe8jBM=";
    };
  };
};

TIP

Leave liteloader.hash blank and rebuild, nix will tell you what hash to use.