backoff

type Backoff struct {
	// InitialInterval is the initial duration to wait before the first retry.
	InitialInterval time.Duration
	// MaxInterval is the upper bound on the backoff duration.
	MaxInterval time.Duration
	// Multiplier is the factor by which the backoff interval increases after each failure.
	Multiplier float64
	// MaxElapsedTime is the maximum total time to spend retrying. If 0, retries indefinitely.
	MaxElapsedTime time.Duration
}

type PermanentError struct {
	Err error
}