code: func LoadX509KeyPair(certFile, keyFile string) (Certificate, error) {
  	certPEMBlock, err := ioutil.ReadFile(certFile)
  	if err != nil {
  		return Certificate{}, err
  	}
  	keyPEMBlock, err := ioutil.ReadFile(keyFile)
  	if err != nil {
  		return Certificate{}, err
  	}
  	return X509KeyPair(certPEMBlock, keyPEMBlock)
  }
docs: // LoadX509KeyPair reads and parses a public/private key pair from a pair of
  // files. The files must contain PEM encoded data. On successful return,
  // Certificate.Leaf will be nil because the parsed form of the certificate is
  // not retained.