code: func (s *Server) ServeTLS(ln net.Listener, certFile, keyFile string) error {
  	err := s.AppendCert(certFile, keyFile)
  	if err != nil && err != errNoCertOrKeyProvided {
  		return err
  	}
  	if s.tlsConfig == nil {
  		return errNoCertOrKeyProvided
  	}
  	s.tlsConfig.BuildNameToCertificate()
  
  	return s.Serve(
  		tls.NewListener(ln, s.tlsConfig),
  	)
  }
docs: // ServeTLS serves HTTPS requests from the given listener.
  //
  // certFile and keyFile are paths to TLS certificate and key files.
  //
  // If the certFile or keyFile has not been provided the server structure,
  // the function will use previously added TLS configuration.