environment

README

Environment variables example

Load all configuration from WEBAPP_* environment variables -- no files needed.

What it shows

• WithEnv("WEBAPP_") as the only source
• Nested structs populated from underscore-separated variable names
• Direct key access with cfg.String(), cfg.Int(), cfg.Bool()
• Automatic string-to-type conversion

Set the variables

export WEBAPP_SERVER_HOST=localhost
export WEBAPP_SERVER_PORT=8080
export WEBAPP_DATABASE_PRIMARY_HOST=db.example.com
export WEBAPP_DATABASE_PRIMARY_PORT=5432
export WEBAPP_DATABASE_PRIMARY_DATABASE=myapp
export WEBAPP_AUTH_JWT_SECRET=your-secret-key
export WEBAPP_FEATURES_DEBUG_MODE=true

Run

cd examples/environment && go run .

Tests

cd examples/environment && go test -v

Expected output

=== Simple Configuration ===
Server: localhost:8080
Database: db.example.com:5432/myapp
Auth JWT Secret: your-secret-key
Debug Mode: true
============================

=== Direct Configuration Access ===
Server: localhost:8080
Database: db.example.com
Debug mode is enabled

How variable names map to keys

Strip the prefix, split on _, and lowercase each part.

Environment variable	Config path	Struct field
WEBAPP_SERVER_HOST	server.host	Server.Host
WEBAPP_DATABASE_PRIMARY_HOST	database.primary.host	Database.Primary.Host
WEBAPP_AUTH_JWT_SECRET	auth.jwt.secret	Auth.JWT.Secret

Key ideas

1. No files required -- environment variables alone are enough.
2. Underscore nesting -- each _ after the prefix creates a deeper level.
3. Type conversion -- string values are converted to the struct field's Go type.
4. Direct access -- you can also read keys with cfg.String("server.host") instead of binding.

Docker example

This pattern follows the Twelve-Factor App methodology and works well with containers:

docker run -e WEBAPP_SERVER_HOST=0.0.0.0 \
           -e WEBAPP_SERVER_PORT=8080 \
           -e WEBAPP_DATABASE_PRIMARY_HOST=prod-db \
           -e WEBAPP_AUTH_JWT_SECRET=prod-secret \
           your-app

Documentation

Overview

Package main demonstrates loading configuration from environment variables with Synthra.