environment

Environment Variables Example

This example demonstrates how to use Config with environment variables for configuration.

Features Demonstrated

• Environment Variable Source: Loading configuration from OS environment variables
• Struct Binding: Mapping environment variables to Go structs
• Nested Configuration: Handling nested configuration structures via environment variables
• Direct Access: Using dot notation to access configuration values
• Type Conversion: Automatic conversion of environment variable strings to Go types

Configuration Structure

The example includes a simple web application configuration:

• Server: Host and port settings
• Database: Primary database connection details
• Authentication: JWT secret configuration
• Features: Debug mode flag

Running the Example

1. Set Environment 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

2. Run the Example

cd examples/environment
go run main.go

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

Environment Variable Naming Convention

Environment variables follow this naming convention:

• Prefix: WEBAPP_ (configurable)
• Hierarchy: Underscores create nested levels
• Conversion: All keys are converted to lowercase

Examples:

Key Concepts

1. Environment Variable Mapping: Environment variables are mapped to configuration paths using underscores
2. Type Safety: String environment variables are automatically converted to appropriate Go types
3. Nested Structures: Deep nesting is supported through underscore-separated environment variable names
4. Direct Access: Use cfg.GetString(), cfg.GetInt(), etc. to access values directly

Production Usage

This pattern is ideal for containerized applications and follows the Twelve-Factor App methodology:

# Docker example
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