Add Docker and Docker Compose support to the fasthttp-postgres quickstart so contributors can run the sample easily without manual setup.

Quickstart link: https://github.com/keploy/samples-go/tree/main/fasthttp-postgres

Tasks

1. Add a Dockerfile inside the fasthttp-postgres quickstart directory

• The Dockerfile should build and run the Go fasthttp application.
• Keep it simple and follow standard Go Docker best practices.

2. Update the docker-compose file

• Add a service for the fasthttp-postgres quickstart.
• Ensure it connects properly with the Postgres service.
• Use environment variables for database configuration.

3. Verify the setup

• The application should start successfully using docker-compose up.
• No manual database or dependency setup should be required.

Expected Outcome

• Contributors can run the fasthttp-postgres quickstart using a single Docker command.
• Postgres runs automatically via Docker Compose.
• The quickstart remains beginner-friendly and easy to understand.

Contribution Notes

• Keep changes limited to the fasthttp-postgres quickstart.
• Anyone is welcome to work on this issue, including first-time contributors.
• Follow the existing project structure and conventions.
• Try to create a PR in the samples-go repo.