add nix mode

init.el

@@ -117,6 +117,9 @@
 ;; langs
 ;;
 
+;; nixos
+(use-package nix-mode :ensure t
+  :mode "\\.nix\\'")
 ;; terraform
 (use-package terraform-mode :ensure t)
 ;; rego
@@ -282,6 +285,15 @@
     :server-id 'php-custom))
   (add-to-list 'lsp-language-id-configuration '(puppet-mode . "php-custom"))
 
+  (lsp-register-client
+   (make-lsp-client
+    :new-connection
+    (lsp-stdio-connection
+     '("nix-shell" "-p" "rnix-lsp" "--run" "rnix-lsp"))
+    :major-modes '(nix-mode)
+    :server-id 'nix))
+  (add-to-list 'lsp-language-id-configuration '(nix-mode . "nix-custom"))
+
   (setq lsp-auto-configure t
         lsp-auto-guess-root t
         lsp-enable-indentation t