# Configuration

> Standards for application configuration using environment variables and libraries.

- Skill: `mte90/configuration` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add mte90/configuration`
- Raw SKILL.md: https://api.skillmd.com/api/skills/mte90/configuration/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: mte90 (https://skillmd.com/u/mte90)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/mte90/configuration

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# Golang Configuration Standards

## **Priority: P1 (STANDARD)**

## Principles

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

## Libraries

- **Standard Lib**: `os.Getenv` for simple apps.
- **Viper**: Industry standard for complex configs (supports env, config files, remote config).
- **Koanf**: Lighter, cleaner alternative to Viper.
- **Caarlos0/env**: Good for strict struct tagging.

## Pattern

1. Define `Config` struct.
2. Load from defaults.
3. Override from file (optional).
4. Override from Env (priority).
5. Validate.

## References

- [Config Pattern](references/config-patterns.md)