code: func ChallengeCert(domain, keyAuth string) (*tls.Certificate, error) {
  	tempCertPEM, rsaPrivatePEM, err := ChallengeBlocks(domain, keyAuth)
  	if err != nil {
  		return nil, err
  	}
  
  	cert, err := tls.X509KeyPair(tempCertPEM, rsaPrivatePEM)
  	if err != nil {
  		return nil, err
  	}
  
  	return &cert, nil
  }
docs: // ChallengeCert returns a certificate with the acmeValidation-v1 extension
  // and domain name for the `tls-alpn-01` challenge.