if err != nil {
		return nil, nil, fmt.Errorf("Failed to create certificate: %w", err)
	}

	certOut := bytes.NewBuffer([]byte{})
	pem.Encode(certOut, &pem.Block{Type: "CERTIFICATE", Bytes: derBytes})

	keyOut := bytes.NewBuffer([]byte{})
	pem.Encode(keyOut, pemBlockForKey(priv))

	return certOut.Bytes(), keyOut.Bytes(), nil
}

    builder then use it to sign another certificate or perform a TLS handshake. The
    `certificatePem()` method encodes the certificate in the familiar PEM format
    (`--- BEGIN CERTIFICATE ---`); the `privateKeyPkcs8Pem()` does likewise for the private key.

    `HandshakeCertificates` holds the TLS certificates required for a TLS handshake. On the server