Configuration

Vukem has no stringly lookups such as config("app.name"). Configuration is read once at boot into typed structs; invalid values abort boot with all problems listed, not only the first one.

.env files#

The config package ships a small, standard-library-only .env parser. Values are resolved with this precedence, highest first:

1. The real process environment
2. .env.<APP_ENV>.local
3. .env.local (skipped when APP_ENV=test, so tests are reproducible)
4. .env.<APP_ENV>
5. .env

APP_NAME=Blog
APP_ENV=development
# Written by vukem key:generate
APP_KEY=base64:your-32-byte-key-in-base64
APP_URL=http://localhost:3000

# ${VAR} interpolation
ASSET_URL=${APP_URL}/build

# Read the value from a file (Docker and Kubernetes secrets)
DB_PASSWORD=@file:/run/secrets/db

# Quotes and escapes
GREETING="Hello\nWorld"
export LOG_LEVEL=debug

Supported syntax: KEY=value, export KEY=value, single and double quotes, \n escapes inside double quotes (values may span lines), # comments, ${OTHER} interpolation and the @file: prefix. The @ keeps SQLite DSNs such as file:storage/app.db untouched.

Per-environment files override .env:

APP_NAME=Blog
APP_ENV=development
APP_KEY=
APP_URL=http://localhost:3000

Core settings#

vukem.New loads the core vukem.Config:

Typed module config#

Fill your own structs with config.Load[T] using env and default tags. Fields of nested structs without an env tag are filled recursively.

type Mail struct {
	Host     string        `env:"MAIL_HOST"     default:"localhost"`
	Port     int           `env:"MAIL_PORT"     default:"1025"`
	From     string        `env:"MAIL_FROM"`
	Password config.Secret `env:"MAIL_PASSWORD"`
	Timeout  time.Duration `env:"MAIL_TIMEOUT"  default:"10s"`
	Cc       []string      `env:"MAIL_CC"` // comma-separated
}

func LoadMail(app *vukem.App) (Mail, error) {
	return config.Load[Mail](app.Source) // every conversion error, joined
}

Supported field types: string, bool, ints, uints, floats, time.Duration, []string (comma-separated), *url.URL, config.Secret and any encoding.TextUnmarshaler.

Testing with a fake environment#

Tests inject configuration instead of calling os.Setenv:

src := config.MapSource(map[string]string{
	"APP_KEY": config.GenerateKey(),
	"APP_ENV": "test",
})

app, err := vukem.New(vukem.WithSource(src))

vukem.WithEnv(fsys, getenv) loads .env files from any fs.FS (for example fstest.MapFS) with a custom getenv.

Secret#

config.Secret holds sensitive values. Every formatting path prints [redacted]: fmt (%v, %s, %#v), encoding/json, encoding.TextMarshaler and log/slog.

cfg.Password.Reveal() // the real value, only where it is used
fmt.Println(cfg.Password)        // [redacted]
app.Log.Info("mail", "cfg", cfg) // password logged as [redacted]

APP_KEY#

• Required. vukem key:generate writes one to .env (creating it from .env.example when missing); --show prints a key instead and --force replaces an existing one, which makes current sessions and encrypted data unreadable. In code, config.GenerateKey() returns 32 random bytes from crypto/rand, base64:-encoded.
• The decoded key is available as app.Key. Never use it directly: derive a purpose-specific key with HKDF-SHA256 so cookies, sessions and encryption never share key material.

sessionKey := app.Key.Derive("session", 32) // HKDF info "vukem:session"

APP_PREVIOUS_KEYS lists former keys (comma-separated, same base64: format) so encrypted cookies and columns survive a rotation; see Encryption.

Secure defaults#