envmodel

Managing configuration data from environment variables using object model.

Usage

Declare model and parse.

package main

import (
	"log"
	"time"

	"github.com/kolatat/envmodel"
)

// Declare the object model
type Config struct {
	Name    string
	Timeout time.Duration
	Debug   bool
}

func main() {
	var cfg Config
	// Parse environment variables into your object
	if _, err := envmodel.Parse(&cfg, &envmodel.Option{
		AppName: "MYAPP",
		DotEnv:  true,
	}); err != nil {
		log.Fatalf("parsing config: %s", err)
	}
}

The parser will read the field names, and convert the PascalCase names into UPPERCASE_SNAKE_CASE names.

Options

Namespace

Namespace - prefixes all key names with the specified namespace. For example, when using Namespace: "DB":

HostName string     => "DB_HOST_NAME"
Database string     => "DB_DATABASE"

DotEnv

DotEnv: true - Additionally loads environment variables from ~.env files. See https://github.com/joho/godotenv.

AppName: "MYAPP" - The environment variable {AppName}_ENV, is checked to establish the runtime environment of the app. If it is empty or unset, a development environment is assumed.

DotEnv will check for and load the following files:

1. .env.{environment}.local
2. .env.local
3. .env.{environment}
4. .env

Missing files will be skipped, and existing variables take precedence.

Struct Tag

Tag key name: env

package main

import "time"

type Config struct {
	Name    string        `env:"key:DISPLAY"`
	Timeout time.Duration `env:"required,default:5s"`
	Wtv     interface{}   `env:"-"`
}

The env tag is a comma separated list of attributes. Use - and the field will be ignored by the parser. Each attribute can be in the form of a flag attribute, or a key-pair key:value.

• key:{string} the name of the environment variable to parse from
• required will throw an error if the variable is not defined and no default is given (an empty string is considered defined)
• default:{string} the value given here will be use in case the variable is undefined (default is not used if the variable is defined but empty i.e "" - the zero value will be assigned)

References

• https://github.com/joho/godotenv
• https://github.com/kelseyhightower/envconfig