If there's no environment config, detect based on environment. sandbox is used for non-production environment. In config.exs, use a string, a function or a tuple. Possible environments are "sandbox", "staging", "production"

config :hit_pay, environment: "sandbox"

or:

config :hit_pay, environment: System.get_env("HIT_PAY_ENVIRONMENT")

or:

config :hit_pay, environment: {:system, "HIT_PAY_ENVIRONMENT"}

or:

config :hit_pay, environment: {MyApp.Config, :HIT_PAY_ENVIRONMENT, []}