A KISS way to deal with environment variables in Go.

At first, it was boring for me to write down an entire function just to get some var from the environment and default to another in case it's missing.

For that manner, I wrote a GetOr function in the go-idioms project.

Then, I got pissed about writing os.Getenv, os.Setenv, os.Unsetenv... it kind of make more sense to me write it as env.Get, env.Set, env.Unset. So I did.

Then I got a better idea: to use struct tags to do all that work for me.

A very basic example (check the examples folder):

package main

import (
	"fmt"
	"time"

	"github.com/caarlos0/env"
)

type config struct {
	Home         string        `env:"HOME"`
	Port         int           `env:"PORT" envDefault:"3000"`
	IsProduction bool          `env:"PRODUCTION"`
	Hosts        []string      `env:"HOSTS" envSeparator:":"`
	Duration     time.Duration `env:"DURATION"`
}

func main() {
	cfg := config{}
	err := env.Parse(&cfg)
	if err != nil {
		fmt.Printf("%+v\n", err)
	}
	fmt.Printf("%+v\n", cfg)
}

You can run it like this:

$ PRODUCTION=true HOSTS="host1:host2:host3" DURATION=1s go run examples/first.go
{Home:/your/home Port:3000 IsProduction:true Hosts:[host1 host2 host3] Duration:1s}

The library has support for the following types:

• string
• int
• uint
• int64
• bool
• float32
• float64
• []string
• []int
• []bool
• []float32
• []float64

If you set the envDefault tag for something, this value will be used in the case of absence of it in the environment. If you don't do that AND the environment variable is also not set, the zero-value of the type will be used: empty for strings, false for bools and 0 for ints.

By default, slice types will split the environment value on ,; you can change this behavior by setting the envSeparator tag.

The env tag option required (e.g., env:"tagKey,required") can be added to ensure that some environment variable is set. In the example above, an error is returned if the config struct is changed to:

type config struct {
    Home         string   `env:"HOME"`
    Port         int      `env:"PORT" envDefault:"3000"`
    IsProduction bool     `env:"PRODUCTION"`
    Hosts        []string `env:"HOSTS" envSeparator:":"`
    SecretKey    string   `env:"SECRET_KEY,required"`
}