fix dockerfile

Author: anthony-nhs

docker/Dockerfile

@@ -33,7 +33,11 @@ ENV PATH="$PATH:/home/cdkuser/.asdf/bin/:/home/cdkuser/node_modules/.bin"
 RUN asdf plugin add nodejs https://github.com/asdf-vm/asdf-nodejs.git
 # install some common node versions that are used in builds to speed things up
 RUN asdf install nodejs 20.19.1; \
-    asdf install nodejs 23.9.0; \
+    asdf install nodejs 23.9.0
+# update npm
+RUN export ASDF_DIR=/home/cdkuser/.asdf && \
+    . /home/cdkuser/.asdf/asdf.sh && \
+    asdf shell nodejs 20.19.1 && \
     cd ~/.asdf/installs/nodejs/20.19.1/lib && npm update npm
 
 # copy files needed for deployment