What?

It demands that a given list of environment variables be set. Optionally, you can specify defaults for them if they're not listed.

How?

import (
  "github.com/davidbanham/required_env"
)
required_env.Ensure(map[string]string{"SOMETHING_IMPORTANT": "", "PORT": "3000"})

Put the above in demo.go and:

go run demo.go Will blow up with the error: "You must specify the env variable SOMETHING_IMPORTANT"

SOMETHING_IMPORTANT=foo go run demo.go Will get you a happily running process in which os.Getenv("PORT") is equal to "3000"

PORT=80 SOMETHING_IMPORTANT=foo go run demo.go Will get you a happily running process in which os.Getenv("PORT") is equal to "80"

Why?

Sometimes when running unfamiliar code it's not obvious what environment variables the author expected to have set. This makes it clearer.

Sometimes when writing code, you want to allow a default option to be overriden by an environment variable. It's tedious to write that code over and over again, though.