React dockerized app: routes not working - reactjs

Question

I am new to Docker and I am trying to dockerize a React app using this Dockerfile:
Dockerfile
FROM node:latest
LABEL autor="Ed de Almeida"
RUN apt-get update && apt-get install -y apache2 tree
RUN mkdir /tmp/myapp
COPY . /tmp/myapp
RUN cd /tmp/myapp && npm install
RUN cd /tmp/myapp && npm run build
RUN cd /tmp/myapp/build && cp -Rvf * /var/www/html
RUN cd /var/www && chown -Rvf www-data:www-data html/
EXPOSE 80
ENV APACHE_RUN_USER www-data
ENV APACHE_RUN_GROUP www-data
ENV APACHE_LOG_DIR /var/log/apache2
ENV APACHE_LOCK_DIR /var/lock/apache2
ENV APACHE_PID_FILE /var/run/apache2.pid
CMD /usr/sbin/apache2ctl -D FOREGROUND
This app uses react-router v4 and it is working perfectly well in my computer when I run it with npm start. It also works fine at Heroku, but there I had to add a static.json file in order to make the routes work, or else I would have only route '/' working and all other routes (like '/admin') would give me a 404.
static.json
{
"root": "build/",
"routes": {
"/**": "index.html"
}
}
By now I have five routes at Heroku:
http://businessfy.herokuapp.com/
http://businessfy.herokuapp.com/admin
http://businessfy.herokuapp.com/admin/usuarios
http://businessfy.herokuapp.com/admin/financeiro
http://businessfy.herokuapp.com/admin/equipe
and they are running fine, going where it expected.
It happend that when I start the container created with the image generated by the Dockerfile above, I only may access '/' and all the routes that are working fine will give me a 404.
I tried to add the static.json file, but it didn't work at all. First I just copied it to the application root directory, just like at Heroku. Nothing changed. Then I tried to import it from my index.js file. Again, nothing changed.
What is the problem here? Am I missing something at Docker? I'm assuming I am, because I am used to React but new to Docker.
Any hints?