get! : Str => Str

Get the value of an environment variable.

Will return empty Str when the variable is not set.

 empty = Env.get!("FAKE_ENV_FOR_SURE_EMPTY")?
 empty |> Assert.should_be("")?

 env = Env.get!("SECRET_ENV_KEY")?
 env |> Assert.should_be("secret_value")?