Upgrade mysql2 gem to latest version with rails 4? - ruby-on-rails-4

Question

i have tried to update mysql2 gem but error are there:
Gem::LoadError: Specified 'mysql2' for database adapter, but the gem is not loaded. Add `gem 'mysql2'` to your Gemfile (and ensure its version is at the minimum required by ActiveRecord).
i have to upgrade mysql2 gem to latest version because i have to do data migration from mysql to postgresql that why we need to upgrade mysql2 gem.
also i need to dump data of mysql database that why i need to upgrade mysql2 gem to latest version.
if any one have suggestion how to done this work so, please help me and mail to: santu.essence#gmail.com
docker file:
FROM ruby:2.7.2
SHELL ["/bin/bash", "-c"]
RUN apt-get update -y --force-yes
RUN apt-get install libtag1-dev -y --force-yes
RUN apt-get install -y curl
RUN curl -sL https://deb.nodesource.com/setup_10.x | bash - \
&& apt-get install nodejs -y
# postgresql-client --- postgresql database adapter
# RUN apt-get install -y wget sudo pgloader
# install ffmpeg
# RUN apt-get install checkinstall
RUN apt-get update \
&& apt-get install -y git build-essential gcc make yasm autoconf automake cmake libtool libmp3lame-dev pkg-config libunwind-dev zlib1g-dev libssl-dev \
&& apt-get update \
&& apt-get clean
RUN apt-get install -y --no-install-recommends libc6-dev libgdiplus wget software-properties-common \
&& wget https://www.ffmpeg.org/releases/ffmpeg-4.0.2.tar.gz \
&& tar -xzf ffmpeg-4.0.2.tar.gz; rm -r ffmpeg-4.0.2.tar.gz \
&& cd ./ffmpeg-4.0.2; ./configure --enable-gpl --enable-libmp3lame --enable-decoder=mjpeg,png --enable-encoder=png --enable-openssl --enable-nonfree \
&& cd ./ffmpeg-4.0.2; make \
&& cd ./ffmpeg-4.0.2; make install \
# ffmpeg installation complete
&& rm -rf /var/lib/apt/lists/*
WORKDIR /usr/src/app
# RUN mkdir -p .bundle && printf '%s\n%s\n' '---' 'BUNDLE_WITHOUT: development:test' > .bundle/config
COPY Gemfile* ./
RUN gem install bundler -v 2.2.28
RUN bundle install
COPY . .
# ENTRYPOINT ./entrypoint-web.sh
docker-compose.yml:
version: '3'
services:
db:
image: mysql:5.6.45
restart: always
environment:
MYSQL_DATABASE: youspin_development
MYSQL_USER: root
MYSQL_PASSWORD: root
MYSQL_ROOT_PASSWORD: root
volumes:
- ./tmp/db:/var/lib/mysql
ports:
- 3306:3306
redis:
image: redis
ports:
- 6379:6379
# volumes:
# ./tmp/db:
# external: true
worker:
# set the path for Dockerfile
build: .
command: bash -c "rm -f /usr/src/app/tmp/pids/resque.pid && rake app:worker-start "
environment:
RAILS_ENV: development
REDIS_URL: redis://redis:6379/0
volumes:
- .:/usr/src/app
depends_on:
- db
- redis
web:
# set the path for Dockerfile
build: .
command: bash -c "rm -f /usr/src/app/tmp/pids/server.pid && rake assets:clobber app:init app:serve && bundle exec rails s -p 3000 -b '0.0.0.0'"
environment:
RAILS_ENV: development
REDIS_URL: redis://redis:6379/0
volumes:
- .:/usr/src/app
ports:
- 3000:3000
depends_on:
- db
- worker
- redis
nginx:
image: nginx
volumes:
- ./config/nginx.dev.conf:/etc/nginx/conf.d/default.conf
- ./public:/var/www/youspin/public
ports:
- 80:80
environment:
- NGINX_PORT=80
links:
- web