My NixOs configuration with xMonad working

configuration.nix

# Edit this configuration file to define what should be installed on
# your system.  Help is available in the configuration.nix(5) man page
# and in the NixOS manual (accessible by running ‘nixos-help’).

{ config, pkgs, ... }:

{
  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
    ];

  # Use the systemd-boot EFI boot loader.
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  networking.hostName = "kodeFant"; # Define your hostname.
  # networking.wireless.enable = true;  # Enables wireless support via wpa_supplicant.
  networking.networkmanager.enable = true;

  # The global useDHCP flag is deprecated, therefore explicitly set to false here.
  # Per-interface useDHCP will be mandatory in the future, so this generated config
  # replicates the default behaviour.
  networking.useDHCP = false;
  networking.interfaces.enp4s0.useDHCP = true;

  # Configure network proxy if necessary
  # networking.proxy.default = "http://user:password@proxy:port/";
  # networking.proxy.noProxy = "127.0.0.1,localhost,internal.domain";

  # Select internationalisation properties.
  i18n.defaultLocale = "en_US.UTF-8";
  console = {
    font = "Lat2-Terminus16";
    keyMap = "us";
  };

  # Set your time zone.
  time.timeZone = "Europe/Amsterdam";

  # List packages installed in system profile. To search, run:
  # $ nix search wget
  environment.variables.EDITOR = "nvim";
  environment.systemPackages = with pkgs; [
    wget
    vscode

    firefox
    google-chrome
    dmenu
    fira-code

    alacritty
    zsh
    oh-my-zsh
    fzf
    silver-searcher

    git
    direnv

    nodejs
    yarn
    vifm-full


    elmPackages.elm
    elmPackages.elm-test
    elmPackages.elm-format
    elmPackages.elm-json


    nodePackages.elm-oracle

    gnumake

    arandr
    feh

    stack
    cabal-install
    stylish-haskell
    haskellPackages.hoogle
    haskellPackages.ghcide
    haskellPackages.gtk2hs-buildtools
    ghcid
    xfce.thunar
  ];


  nixpkgs.config.allowUnfree = true;

  nixpkgs.overlays = [
   (self: super: {
     neovim = super.neovim.override {
       viAlias = true;
       vimAlias = true;
     };
   })
  ];

  fonts.fonts = with pkgs; [
    fira-code fira-mono
  ];

  programs.zsh = {
    enable = true;
    enableCompletion = true;
    ohMyZsh.theme = "lambda";
    ohMyZsh.enable = true;
    ohMyZsh.plugins = [ "git" ];
    autosuggestions.enable = true;
    syntaxHighlighting.enable = true;
  };

  # Some programs need SUID wrappers, can be configured further or are
  # started in user sessions.
  # programs.mtr.enable = true;
  # programs.gnupg.agent = {
  #   enable = true;
  #   enableSSHSupport = true;
  #   pinentryFlavor = "gnome3";
  # };

  # List services that you want to enable:

  # Enable the OpenSSH daemon.
  # services.openssh.enable = true;

  # Open ports in the firewall.
  # networking.firewall.allowedTCPPorts = [ ... ];
  # networking.firewall.allowedUDPPorts = [ ... ];
  # Or disable the firewall altogether.
  # networking.firewall.enable = false;

  # Enable CUPS to print documents.
  # services.printing.enable = true;

  # Enable sound.
  sound.enable = true;
  hardware.pulseaudio.enable = true;

  # Enable the X11 windowing system.
  services.autorandr.enable = true;
  services.xserver = {
    enable = true;
    autorun = true;
    layout = "us,no";
    xkbModel = "pc105";
    xkbOptions = "eurosign:e, compose:menu, grp:caps_toggle";
    videoDrivers = [ "nvidia" ];
    xrandrHeads = [{output = "HDMI-0";primary = true;}{output = "VGA-0";}];
    windowManager = {
      xmonad = {
        enable = true;
        enableContribAndExtras = true;
        extraPackages = hpkgs: [
          hpkgs.xmobar
          hpkgs.xmonad-screenshot
        ];
      };
    };
    displayManager = {
      defaultSession = "none+xmonad";
      lightdm = {
        greeters.enso = {
          enable = true;
          blur = true;
          extraConfig = ''
            default-wallpaper=/usr/share/streets_of_gruvbox.png
          '';
        };
      };
      sessionCommands = ''
        xrandr --output VGA-0 --mode 1400x900 --pos 2560x336 --rotate normal --output DVI-D-0 --off --output HDMI-0 --primary --mode 2560x1440 --pos 0x0 --rotate normal
        ./.fehbg
        '';
    };
  };

  # Enable touchpad support.
  # services.xserver.libinput.enable = true;

  # Define a user account. Don't forget to set a password with ‘passwd’.
  users.users.lillo = {
     isNormalUser = true;
     extraGroups = [ "wheel" "networkmanager" ]; # Enable ‘sudo’ for the user.
     shell = pkgs.zsh;
  };

  nix.trustedUsers = ["root" "lillo"];

  # This value determines the NixOS release from which the default
  # settings for stateful data, like file locations and database versions
  # on your system were taken. It‘s perfectly fine and recommended to leave
  # this value at the release version of the first install of this system.
  # Before changing this value read the documentation for this option
  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
  system.stateVersion = "unstable"; # Did you read the comment?

}