.env Loading With Flag Control

I like having .env support for local development when developing web service. It's simple, and encourages implementation to consider configurability through environment variables.

More importantly for me it offers development portability whenever I need to move around OS doing development, because I may not have good shell always ready.

This is referential setup to support .env loading in Go that doesn't get in the way of production release to ease project bootstrapping chores.

Implementation Checklist

• Provide .env.example
• Add .env to .gitignore
• Add .env to .dockerignore for containerized workflow
• Register -env flag in the project flag parsing logic, prefer allowing to override .env path with .env as default if unspecified
• Prefer .env loading logic at the beginning main function as early as possible after flag parsing.
• Modify .air.toml or other live-reload config to -env flag by default. See .air.toml for reference
• Ensure .env loading is non-default behavior without the flag

# Load .env in root repository
go run . -env

# Load .env in nested path within repo
go run . -env=nested_env_example/.env