webapp

README

Web application example (layered config)

A realistic setup: YAML defaults, WEBAPP_* environment overrides, struct binding, and a Validate method on the bound struct.

What it shows

• Layered sources -- WithFile first, then WithEnv (later source wins on conflicts)
• Deeply nested YAML matching nested struct tags (server.tls.cert.file, etc.)
• Direct key access with dot paths (cfg.String("server.host"))
• Struct-level validation via the synthra.Validator interface
• Tests for env-only, YAML-only, layered precedence, and validation failures

Run

cd examples/webapp && go run .

Tests

cd examples/webapp && go test -v

Load keys from your shell (optional)

source examples/webapp/setup_env.sh
cd examples/webapp && go run .

Production-style construction

cfg, err := synthra.New(
    synthra.WithFile("config.yaml"),
    synthra.WithEnv("WEBAPP_"),
    synthra.WithBinding(&appConfig),
)
if err != nil {
    log.Fatal(err)
}
if err := cfg.Load(ctx); err != nil {
    log.Fatal(err)
}

Baking defaults into the binary

To embed defaults directly in the binary instead of shipping a separate config.yaml, prepend synthra.WithContent as the lowest-priority source:

cfg := synthra.MustNew(
    synthra.WithContent(defaultYAML, codec.YAML), // lowest priority
    synthra.WithFile("config.yaml"),               // overrides defaults
    synthra.WithEnv("WEBAPP_"),                    // highest priority
    synthra.WithBinding(&appConfig),
)

The same merge rules apply: each source overrides keys from all earlier sources.

How environment variables map to keys

Strip the WEBAPP_ prefix, split on _, lowercase.

Variable	Config key
WEBAPP_SERVER_PORT	server.port
WEBAPP_SERVER_TLS_ENABLED	server.tls.enabled
WEBAPP_DATABASE_PRIMARY_HOST	database.primary.host
WEBAPP_AUTH_JWT_SECRET	auth.jwt.secret
WEBAPP_FEATURES_DEBUG_MODE	features.debug.mode

Docker (optional)

From the repository root (see examples/Dockerfile):

docker build -f examples/Dockerfile -t synthra-webapp-example .
docker run --rm synthra-webapp-example

Override values at runtime with -e WEBAPP_SERVER_PORT=8080, and so on.

Documentation

Overview

Package main demonstrates layered configuration (YAML defaults plus environment overrides), struct binding, and validation with Synthra.