Fixing pusher dockerfile

pusher/Dockerfile

@@ -1,6 +1,12 @@
+FROM thecodingmachine/workadventure-back-base:latest as builder
+WORKDIR /var/www/messages
+COPY --chown=docker:docker messages .
+RUN yarn install && yarn proto
+
 FROM thecodingmachine/nodejs:12
 
 COPY --chown=docker:docker pusher .
+COPY --from=builder --chown=docker:docker /var/www/messages/generated /usr/src/app/src/Messages/generated
 RUN yarn install
 
 ENV NODE_ENV=production