Env

Small and strict environment variable helpers for Go. Designed for microservices and containerized applications where configuration should be explicit, predictable, and fail-fast.

Install

go get github.com/nasermirzaei89/env

Sample Usage

With default value

package main

import (
	"fmt"
	"time"

	"github.com/nasermirzaei89/env"
)

func main() {
	b := env.GetBool("A", true)
	fmt.Println(b) // true (default)

	f := env.GetFloat64("B", 14.5)
	fmt.Println(f) // 14.5 (default)

	i := env.GetInt("C", 12)
	fmt.Println(i) // 12 (default)

	s := env.GetString("B", "hi")
	fmt.Println(s) // hi (default)

	d := env.GetDuration("D", 5*time.Second)
	fmt.Println(d) // 5s (default)

	// With generics

	b2 := env.Get("A", true)
	fmt.Println(b2) // true (default)

	f2 := env.Get("B", 14.5)
	fmt.Println(f2) // 14.5 (default)

	i2 := env.Get("C", 12)
	fmt.Println(i2) // 12 (default)

	s2 := env.Get("B", "hi")
	fmt.Println(s2) // hi (default)

	d2 := env.Get("D", 5*time.Second)
	fmt.Println(d2) // 5s (default)
}

Force setting environment

package main

import (
	"fmt"
	"time"

	"github.com/nasermirzaei89/env"
)

func main() {
	s := env.MustGetString("HOME")
	fmt.Println(s) // /Users/nasermirzaei89

	s = env.MustGetString("NEW") // panics

	d := env.MustGetDuration("TIMEOUT")
	fmt.Println(d) // e.g. 30s

	d = env.MustGetDuration("NEW") // panics

	// Generics

	s2 := env.MustGet[string]("HOME")
	fmt.Println(s2) // /Users/nasermirzaei89

	s2 = env.MustGet[string]("NEW") // panics

	d2 := env.MustGet[time.Duration]("TIMEOUT")
	fmt.Println(d2) // e.g. 30s

	d2 = env.MustGet[time.Duration]("NEW") // panics
}

Lookup with structured errors

LookupXXX returns the value and an error. Use errors.As to distinguish between a missing key (NotSetError) and an unparseable value (InvalidValueError).

package main

import (
	"errors"
	"fmt"
	"time"

	"github.com/nasermirzaei89/env"
)

func main() {
	// Typed lookup
	v, err := env.LookupInt("PORT")
	if err != nil {
		var notSet env.NotSetError
		var invalid env.InvalidValueError

		switch {
		case errors.As(err, &notSet):
			fmt.Printf("%q is not set\n", notSet.Key)
		case errors.As(err, &invalid):
			fmt.Printf("%q has invalid value %q: %v\n", invalid.Key, invalid.Value, invalid.Err)
		}
	} else {
		fmt.Println("PORT =", v)
	}

	// Generic lookup
	s, err := env.Lookup[string]("HOME")
	if err == nil {
		fmt.Println("HOME =", s)
	}
}

Contributing

You can submit a new issue in GitHub issues. Or you can create a fork, hack on your fork and when you're done create a pull request, so that the code contribution can get merged into the main package.