config

github.com/Tech-Arch1tect/config

An extremely simple library to load configurations from environment variables and .env files.

Features

• Environment Variable Loading: Load configuration from environment variables
• .env File Support: Automatically loads variables from a .env file
• Environment Override: Environment variables take precedence over .env file values
• Validation: Comprehensive (not yet!) validation rules for configuration values
• Default Values: Set default values through the SetDefaults method
• No External Dependencies: Pure Go implementation

Supported Validations (more to come)

• required: Ensures a value is provided.
• min: Checks that a numeric value is greater than or equal to a minimum, or that a string has at least the minimum number of characters.
• max: Checks that a numeric value is less than or equal to a maximum, or that a string does not exceed the maximum number of characters.
• email: Validates that a string is a properly formatted email address.
• url: Validates that a string is a properly formatted URL.
• regexp: Validates that a string matches a given regular expression pattern.
• in: Validates that a string is one of a set of allowed values, using the pipe (|) character as a delimiter.
• not_in: Validates that a string is not one of a set of disallowed values, using the pipe (|) character as a delimiter.
• eq: Validates that a string is equal to a specified value.
• ne: Validates that a string is not equal to a specified value.

Installation

go get github.com/Tech-Arch1tect/config

Usage

Define your configuration struct and provide default values by implementing the SetDefaults method.

package main

import (
    "fmt"
    "log"

    "github.com/Tech-Arch1tect/config"
)

type AppConfig struct {
    AppName string `env:"APP_NAME" validate:"required,min=10"`
    Port    int    `env:"PORT" validate:"required,max=65535"`
    Email   string `env:"APP_EMAIL" validate:"required,email"`
}

func (c *AppConfig) SetDefaults() {
    c.AppName = "Default App"
    c.Port = 8080
    c.Email = "default@example.com"
}

func main() {
    var cfg AppConfig
    if err := config.Load(&cfg); err != nil {
        log.Fatalf("Failed to load config: %v", err)
    }
    fmt.Printf("Loaded configuration: %+v\n", cfg)
}

.env File Support

The library automatically loads environment variables from a .env file in the current directory. The .env file format supports:

• Simple key=value pairs
• Quoted values (both single and double quotes)
• Comments (lines starting with #)
• Empty lines (ignored)

Example .env file:

# Application Configuration
APP_NAME="My Application"
PORT=3000
DEBUG=true
DATABASE_URL='postgres://user:pass@localhost/mydb'

# Email Configuration
APP_EMAIL=admin@example.com

Priority Order

Configuration values are loaded in the following priority order (highest to lowest):

1. Environment Variables - Values set in the actual environment
2. .env File - Values from the .env file
3. Default Values - Values set in the SetDefaults() method

This means environment variables will always override .env file values, and .env file values will override defaults.

Example with .env file:

.env file:

APP_NAME=EnvFileApp
PORT=3000

Environment variable:

export APP_NAME=EnvironmentApp

Result:

• APP_NAME will be "EnvironmentApp" (from environment variable)
• PORT will be 3000 (from .env file)
• EMAIL will be "default@example.com" (from defaults)

How It Works

• .env File Loading:
  The library first reads a .env file from the current directory (if it exists). Variables from this file are set in the environment only if they don't already exist.

• Environment Variable Loading:
  The library scans your struct for env tags and assigns the corresponding environment variable values. If an environment variable is not set, the SetDefaults method provides fallback values.

• Validation:
  After loading the configuration, the library validates the struct using the validate tags described above.

Error Handling

• If the .env file doesn't exist, the library continues without error
• If the .env file exists but has parsing errors, the library will return an error
• Validation errors are returned if any configured validation rules fail