defaults

README

Embedded defaults (WithContent)

Bake default values into your binary, override them with a file, then let environment variables win last.

Sources are merged in order -- later values replace earlier ones:

1. WithContent -- small YAML defaults embedded in Go code
2. WithFile("overrides.yaml") -- checked-in overrides
3. WithEnv("DEMO_") -- highest precedence

Run

cd examples/defaults
DEMO_SERVER_PORT=9999 go run .

Expected output: server.name=from-file server.port=9999

• server.name comes from overrides.yaml (replaced the baked-in default)
• server.port comes from the DEMO_SERVER_PORT env var (replaced the file value of 7000)

Tests

cd examples/defaults && go test -v

Key ideas

1. Merge order matters -- sources added later override earlier ones on the same key.
2. Embedded defaults -- WithContent takes a []byte and a codec, so you can use go:embed or a literal.
3. Three layers -- defaults, file, environment is a common production pattern.

Documentation

Overview

Package main shows merge order: baked-in defaults, then file, then env.