enhance: add functions for daemon servers for mTLS

[g-linville]

Here is an example of what it looks like to use these functions:

package main

import (
	"fmt"
	"net/http"
	"os"

	"github.com/gptscript-ai/go-gptscript/pkg/daemon"
)

func main() {
	server, err := daemon.CreateServer()
	if err != nil {
		fmt.Printf("failed to create server: %v\n", err)
		os.Exit(1)
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		clientCert := r.TLS.PeerCertificates[0]
		fmt.Fprintf(w, "Hello, %s\n", clientCert.Subject.CommonName)
	})

	if err := daemon.StartServer(server); err != nil {
		fmt.Printf("failed to start server: %v\n", err)
		os.Exit(1)
	}
}

[thedadams]

I'm fine with the two functions for creating a server, but it seems strange to call CreateServer(), add a bunch of stuff to the default http server mux, and then StartServer.

Instead of returning an *http.Server, can we return our own server type that has methods like the http.ServerMux that just passes them onto an *http.ServerMux field on the server type. Something like:

type Server struct {
 	 mux *http.ServeMux
 	 tlsConfig *tls.Config
 	 port string
}

func CreateServer(port string) (*Server, error) {
 	retrurn CreateServerWithMux(http.DefaultServeMux, port)
 }

func CreateServerWithMux(mux *http.ServeMux, port string) (*Server, error) {
 	tlsConfig, err := getTLSConfig()
 	if err != nil {
 		return nil, fmt.Errorf("failed to get TLS config: %v", err)
 	}

 	 server := &Server{
 	  	 tlsConfig: tlsConfig,
 	  	 port: port,
 	  	 mux: mux,
 	 }
 	return server, nil
 }

func (s *Server) HandleFunc(patter string, handler http.HandlerFunc) {
 	 s.mux.HandleFunc(pattern, handler)
}

[thedadams]

ListenAndServerTLS always returns a non-nil error. We may want to check for http.ErrServerClosed because that would be expected, I think.

[g-linville]

fixed

[thedadams]

We probably want to make the port a parameter. Otherwise, you could only ever run one daemon at a time.

[g-linville]

But we do only want to run one daemon at a time, at least one per process, and it is required to use the port that GPTScript chose for it. So I don't think there is a point in making this a parameter. This is just a library function to be called in each daemon tool, not something that will get used anywhere else.