Force update all channels before upgrade

configuration.nix

@@ -60,6 +60,10 @@ in {
     };
   };
 
+  # force update all channels
+  systemd.services.nixos-upgrade.serviceConfig.ExecStartPre =
+    "${pkgs.nix}/bin/nix-channel --update";
+
   systemd.services.nixos-upgrade.serviceConfig.ExecStartPost = pkgs.writeScript "post-upgrade-check" ''
     #!${pkgs.stdenv.shell}
     current=$(readlink -f /run/current-system/kernel)