const (
	// browserCSPPolicy setting name for Content-Security-Policy response header value
	browserCSPPolicy = "csp_policy"
	// browserHSTSSeconds setting name for Strict-Transport-Security response header, amount of seconds for 'max-age'
	browserHSTSSeconds = "hsts_seconds"
	// browserHSTSIncludeSubdomains setting name for Strict-Transport-Security response header 'includeSubDomains' flag (true or false)

	// if TTL has expired but 2x TTL has not yet passed,
	// but will fetch a new value in the background.
	NoWait bool
}

// Cache contains a synchronized value that is considered valid
// for a specific amount of time.
// An Update function must be set to provide an updated value when needed.
type Cache[T any] struct {
	// updateFn must return an updated value.
	// If an error is returned the cached value is not set.