Use variable for 8123 port setting

start_container.sh

@@ -5,9 +5,11 @@
 # `-o pipefail`: Prevent errors in a pipeline (`|`) from being masked
 set -uo pipefail
 
+declare -r APP_PORT=8123
+
 # Import environment variables from .env
 set -o allexport && source .env && set +o allexport
-echo "Starting container for image '$DOCKER_IMAGE_NAME:$DOCKER_IMAGE_TAG', exposing port 8123/tcp"
-echo "- Run 'curl http://localhost:8123/status' to send a test request to the containerized app."
+echo "Starting container for image '$DOCKER_IMAGE_NAME:$DOCKER_IMAGE_TAG', exposing port ${APP_PORT}/tcp"
+echo "- Run 'curl http://localhost:${APP_PORT}/status' to send a test request to the containerized app."
 echo "- Enter Ctrl-C to stop the container."
-docker run -p 8123:8123 "$DOCKER_IMAGE_NAME":"$DOCKER_IMAGE_TAG"
+docker run -p "$APP_PORT:$APP_PORT" "$DOCKER_IMAGE_NAME":"$DOCKER_IMAGE_TAG"