envconfig

Package envconfig will populate your config struct based on sources such as environment variables, files, etc.

• Installation
• Features
  • Options
  • Struct Tags
  • Other
  • Examples
• Merging Values

Installation

go get github.com/h-dav/envconfig/v3

Features

Options

Option	Description
WithFilepath("config/file.env")	Use file to populate config struct.
WithActiveProfile("dev_env")	Provide the profile to select a specific config file.

Struct Tags

• env: Used to determine the key of the value to use when populating config fields.
• required: true or false
• default: Default value if environment variable is not set.
• prefix: Used for nested structures.
• envjson: Used for deserialising JSON into config.

Other

• Text Replacement: ${EXAMPLE} can be used to insert other discovered values.

Merging Values

Important

When merging values, envconfig uses the following precedence:

1. Flags
2. Environment Variables
3. Config File (provided via WithFilepath())

Examples

Basic

func main() {
    type Config struct {
        Development bool `env:"DEVELOPMENT" default:"true"`
    }

    var cfg Config

    if err := envconfig.Set(&cfg); err != nil {
        panic(err)
    }
}

Config File

func main() {
    type Config struct {
        Service string `env:"SERVICE"`
    }

    var cfg Config

    if err := envconfig.Set(&cfg, WithFilepath("internal/config/config.env")); err != nil {
        panic(err)
    }
}

Profile

func main() {
    type Config struct {
        Service string `env:"SERVICE"`
    }

    var cfg Config

    if err := envconfig.Set(
        &cfg,
        WithActiveProfile(os.Getenv("ACTIVE_PROFILE")),
        WithFilepath("internal/config/"), // Will use file `internal/config/development.env`.
    ); err != nil {
        panic(err)
    }
}

Nested Structs

func main() {
    type Config struct {
        Service struct {
            Name string `env:"NAME"`
            Version string `env:"VERSION"`
        } `prefix:"SERVICE_"`
    }

    var cfg Config

    if err := envconfig.Set(&cfg); err != nil {
        panic(err)
    }
}