Dockerfile
FROM ruby:2.5
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev
# Node.js
RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - \
&& apt-get install -yq nodejs
RUN npm i -g npm
# yarn
RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -\
&& echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list \
&& apt-get update \
&& apt-get install -y yarn
RUN mkdir /app
WORKDIR /app
COPY Gemfile Gemfile.lock /app/
RUN bundle install
ADD . /app