func WithRootCAs(path string) Option {
	return func(settings *clientSettings) error {
		settings.caCerts = x509.NewCertPool()
		return addCertFromFile(settings.caCerts, path)
	}
}
func WithRootCAs(path string) Option {
	return func(settings *clientSettings) error {
		settings.caCerts = x509.NewCertPool()
		return addCertFromFile(settings.caCerts, path)
	}
}
// WithRootCAs instructs the New* functions to create client that uses the
// given signed x509 certificates as the trusted root certificates (instead of
// the system certs). Introduced to pass certs provided via command-line flags