Container Sigterm Not Triggered

I am trying to make a container that saves data on exit.
However, it doesn’t trigger the trapped command.
This is the ENTRYPOINT of the Dockerfile:

ENTRYPOINT ["/bin/bash","start.sh"]

start.sh:

trap 'echo "replace with command that copy data"' SIGTERM
echo "Exit Proc Ready"
# Actual Code Goes Here
wait $!