server.go
func (s *Server) AppendCert(certFile, keyFile string) error {
	if len(certFile) == 0 && len(keyFile) == 0 {
		return errNoCertOrKeyProvided
	}

	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
	if err != nil {
		return fmt.Errorf("cannot load TLS key pair from certFile=%q and keyFile=%q: %s", certFile, keyFile, err)
	}

	s.configTLS()

	s.tlsConfig.Certificates = append(s.tlsConfig.Certificates, cert)
	return nil
}
func (s *Server) AppendCert(certFile, keyFile string) error {
	if len(certFile) == 0 && len(keyFile) == 0 {
		return errNoCertOrKeyProvided
	}

	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
	if err != nil {
		return fmt.Errorf("cannot load TLS key pair from certFile=%q and keyFile=%q: %s", certFile, keyFile, err)
	}

	s.configTLS()

	s.tlsConfig.Certificates = append(s.tlsConfig.Certificates, cert)
	return nil
}
// AppendCert appends certificate and keyfile to TLS Configuration.
//
// This function allows programmer to handle multiple domains
// in one server structure. See examples/multidomain