Golang Configuration

Priority: P1 (STANDARD)

Principles

• 12-Factor App: Store config in environment variables.
• Typed Config: Load config into a struct, validate immediately.
• Secrets: Never commit secrets. Use env vars or secret managers.
• No Globals: Return a Config struct and inject it.

Implementation Workflow

1. Define Config struct — Create a typed struct with all required fields.
2. Load defaults — Set sensible defaults for non-secret values.
3. Override from file — Optionally load from YAML/JSON config file.
4. Override from env — Environment variables take highest priority.
5. Validate at startup — Crash immediately on missing required config.
6. Inject via constructor — Pass Config to services; never use global config vars.

See config struct and usage examples

Libraries

• Standard Lib: os.Getenv for simple apps.
• Viper: Industry standard for complex configs (env, files, remote).
• Koanf: Lighter, cleaner alternative to Viper.
• Caarlos0/env: Strict struct tagging approach.

Anti-Patterns

• ❌ Hardcoded secrets — load all secrets from env vars or a secret manager
• ❌ Global config variables — return a typed Config struct and inject via constructors
• ❌ Starting without validation — crash immediately on missing required env vars

References

• Config Pattern