Config

A Go package that provides functionality for loading application configuration from environment variables with support for .env files.

This module is a wrapper around godotenv and envconfig (see Dependencies section below)

Features

• Load environment variables from multiple .env files
• Process environment variables into Go structs
• Support for required fields and default values
• Prefix support for environment variables
• Helpful error messages for missing required variables
• Functional options pattern for flexible configuration

Installation

go get github.com/twlvprscs/config

Usage

Basic Usage

package main

import (
    "log"
    
    "github.com/twlvprscs/config"
)

// Define your configuration struct with appropriate tags
type AppConfig struct {
    DatabaseURL string `envconfig:"DATABASE_URL" required:"true"`
    Port        int    `envconfig:"PORT" default:"8080"`
    Debug       bool   `envconfig:"DEBUG" default:"false"`
}

func main() {
    // Create an instance of your config struct
    var cfg AppConfig
    
    // Load configuration
    err := config.Load(
        config.WithPrefix("APP"),
        config.WithEnvFiles(".env", ".env.local"),
        config.WithConfigs(&cfg),
    )
    if err != nil {
        log.Fatalf("Failed to load config: %v", err)
    }
    
    // Use your configuration
    log.Printf("Database URL: %s", cfg.DatabaseURL)
    log.Printf("Port: %d", cfg.Port)
    log.Printf("Debug mode: %v", cfg.Debug)
}

Environment Variables

With the above example, the package will look for the following environment variables:

• APP_DATABASE_URL (required)
• APP_PORT (defaults to 8080 if not set)
• APP_DEBUG (defaults to false if not set)

.env File Example

APP_DATABASE_URL=postgres://user:pass@localhost:5432/db
APP_DEBUG=true

Options

WithPrefix

Sets a prefix for environment variables. This is useful for namespacing configuration for different parts of an application.

config.WithPrefix("APP")

WithEnvFiles

Specifies one or more .env files to load environment variables from. Files are loaded in the order specified, with later files taking precedence over earlier ones.

config.WithEnvFiles(".env", ".env.local")

WithConfigs

Specifies one or more configuration structs to populate with values from environment variables.

config.WithConfigs(&cfg1, &cfg2)

Error Handling

The package provides helpful error messages for missing required variables:

err := config.Load(...)
if errors.Is(err, config.ErrMissingEnvVar) {
    // Handle missing environment variable
    log.Fatalf("Missing environment variable: %v", err)
}

Dependencies

• github.com/joho/godotenv - For loading environment variables from .env files
• github.com/kelseyhightower/envconfig - For processing environment variables into Go structs

License

This project is licensed under the MIT License - see the LICENSE file for details.