GetenvBool returns true if and only if the environment variable with the given key exists and contains a string that strconv.ParseBool() recognizes as true.

GetenvOrDefault returns os.Getenv(key), except that if the environment variable is not set, the given default value will be returned instead.

NeedGetenv returns os.Getenv(key), or panics if the environment variable is not set.

NeedGetenv returns os.Getenv(key), or an error if the environment variable is not set.

MissingEnvError is an error that occurs when an required environment variable was not present.