golang http server handler and pointer issue - http

Question

I am a bit lost with go-routines, http server, handlers and pointers.
I ve created a http server that accepts any request at any path, I am starting it in separate routine so main thread is not blocked
// main thread
// I want to bind to random port and read port later
listener, err := net.Listen("tcp", ":0")
rh := requestHandler{} // look at point 2)
s := &http.Server{
Handler: rh,
ReadTimeout: 10 * time.Second,
WriteTimeout: 10 * time.Second,
MaxHeaderBytes: 1 << 20,
}
go func() {
err := s.Serve(listener)
...
}()
rh is a Handler interface so I ve created a struct following the interface
type requestHandler struct {
values []string
}
func (rh requestHandler) ServeHTTP(w http.ResponseWriter, givenRequest *http.Request) {
log.Println("DEBUG : handling request", givenRequest.Method, givenRequest.URL, givenRequest.RequestURI)
log.Println("DEBUG : headers", givenRequest.Header)
for _, value := range rh.values { // <----- values are always empty
}
}
lets add some values to handler
// main thread
rh.values = append(rh.values, "one)
obviously this doesn't work as Server is copying Handler and rh variable from main thread has different pointer than s.Handler, but this is OK.
What I dont understand is that also rh in func (rh requestHandler) ServeHTTP(w http.ResponseWriter, givenRequest *http.Request) has different pointer than s.Handler.
how can I pass anything to requestHandler.values from main thread so those values can be read in callback function ? I ve tried using channels but I cannot access pointer/ref to right rh. Is it because each request is also spawn in new routine and handler is also copied ?
sample code
type MyServer struct {
Port int
pid *http.Server
requestHandler requestHandler
}
func (s *MyServer) addValue(value string) {
s.requestHandler.values = append(s.requestHandler.values, value)
}
func InitializeServer() *MyServer {
rh := requestHandler{}
listener := bindToNextFreePort()
s := &http.Server{
Handler: rh,
ReadTimeout: 10 * time.Second,
WriteTimeout: 10 * time.Second,
MaxHeaderBytes: 1 << 20,
}
startServer(s, listener)
currentPort := getTcpPort(listener)
log.Println("My Server Initialized on ", currentPort)
return &MyServer{
pid: s,
Port: currentPort,
requestHandler: rh,
}
}
func startServer(s *http.Server, listener net.Listener) {
go func() {
log.Println("starting Mock Server")
err := s.Serve(listener)
}()
}
type requestHandler struct {
values []string
}
func (rh requestHandler) ServeHTTP(w http.ResponseWriter, givenRequest *http.Request) {
log.Println("DEBUG : handling request", givenRequest.Method, givenRequest.URL, givenRequest.RequestURI)
log.Println("DEBUG : headers", givenRequest.Header)
for key, value := range rh.values {
}
}
func bindToNextFreePort() net.Listener {
listener, err := net.Listen("tcp", ":0")
if err != nil {
panic(err)
}
return listener
}

Answer 1

It turned out to be quite simple, I've closed my eyes for this assignment here
return &MyServer{
pid: s,
Port: currentPort,
requestHandler: rh,
}
Which led to yet another copy.