Steps:

• Download the json file of countries from here.
• Change the name to countries.json & place it in the /resources directory
• Make sure you have Docker installed on your computer
• Simply run the run.sh file like ./run.sh
• If you can not run bash file then just manually run the docker-compose to start the required services and then mvn spring-boot:run
• Since I'm running the project in Ubuntu, it may not be compatible with other operating systems, but it's not a big deal at all.