code: func (s *Server) SetQuicHeaders(hdr http.Header) error {
  	port := atomic.LoadUint32(&s.port)
  
  	if port == 0 {
  		// Extract port from s.Server.Addr
  		_, portStr, err := net.SplitHostPort(s.Server.Addr)
  		if err != nil {
  			return err
  		}
  		portInt, err := net.LookupPort("tcp", portStr)
  		if err != nil {
  			return err
  		}
  		port = uint32(portInt)
  		atomic.StoreUint32(&s.port, port)
  	}
  
  	if s.supportedVersionsAsString == "" {
  		var versions []string
  		for _, v := range protocol.SupportedVersions {
  			versions = append(versions, v.ToAltSvc())
  		}
  		s.supportedVersionsAsString = strings.Join(versions, ",")
  	}
  
  	hdr.Add("Alt-Svc", fmt.Sprintf(`quic=":%d"; ma=2592000; v="%s"`, port, s.supportedVersionsAsString))
  
  	return nil
  }
docs: // SetQuicHeaders can be used to set the proper headers that announce that this server supports QUIC.
  // The values that are set depend on the port information from s.Server.Addr, and currently look like this (if Addr has port 443):
  //  Alt-Svc: quic=":443"; ma=2592000; v="33,32,31,30"