Overview

fig loads configuration from environment variables, secret providers, and defaults using Go struct tags.

The Idea

Configuration should be declarative. You define what a field needs—its source, its default, whether it's required—and the library handles the rest. No builder chains, no option structs, no multi-step initialization. One function call, predictable resolution order.

The Implementation

fig provides:

• Struct tag parsing — env, secret, default, and required tags
• Deterministic resolution — secret → env → default → zero value, every time
• Secret provider abstraction — plug in Vault, AWS Secrets Manager, GCP Secret Manager, or your own
• Type conversion — strings, ints, floats, bools, durations, slices, and TextUnmarshaler
• Validation hooks — implement Validator for post-load checks
• Nested struct support — automatic recursion into embedded configurations

What It Enables

• Single-source-of-truth configuration structs
• Secure secret injection without environment variable sprawl
• Testable configuration with mock providers
• Consistent loading across services in a microservices architecture

fig integrates with:

• HashiCorp Vault — KV secrets engine
• AWS Secrets Manager — standard AWS credential chain
• GCP Secret Manager — project-scoped secrets

Next Steps

• Quickstart — get productive in minutes
• Concepts — understand resolution order and struct tags
• Reference — full API documentation