README: fix node name look-up

README.md

@@ -13,10 +13,13 @@ Afterwards, create a `default.nix` file containing the following:
 ```nix
 (import
   (
-    let lock = builtins.fromJSON (builtins.readFile ./flake.lock); in
+    let
+      lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+      nodeName = lock.nodes.root.inputs.flake-compat;
+    in
     fetchTarball {
-      url = lock.nodes.flake-compat.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      url = lock.nodes.${nodeName}.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.${nodeName}.locked.rev}.tar.gz";
-      sha256 = lock.nodes.flake-compat.locked.narHash;
+      sha256 = lock.nodes.${nodeName}.locked.narHash;
     }
   )
   { src = ./.; }