Update dockerfile

The value EXPOSED_PORT need to be declared before use

docker/Dockerfile

@@ -3,6 +3,7 @@ VOLUME /tmp
 ADD https://raw.githubusercontent.com/vishnubob/wait-for-it/master/wait-for-it.sh wait-for-it.sh
 RUN bash -c 'chmod +x wait-for-it.sh'
 ARG ARTIFACT_NAME
+ARG EXPOSED_PORT
 ADD ${ARTIFACT_NAME}.jar /app.jar
 ENV SPRING_PROFILES_ACTIVE docker
 RUN bash -c 'touch /app.jar'