allow to have custom http.Server struct

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

http.go

@@ -376,6 +376,8 @@ func (h *httpServer) Start() error {
 	}
 
 	fn := handler
+	var srvFunc func(net.Listener) error
+
 	if h.opts.Context != nil {
 		if mwf, ok := h.opts.Context.Value(middlewareKey{}).([]func(http.Handler) http.Handler); ok && len(mwf) > 0 {
 			// wrap the handler func
@@ -383,9 +385,17 @@ func (h *httpServer) Start() error {
 				fn = mwf[i-1](fn)
 			}
 		}
+		if hs, ok := h.opts.Context.Value(serverKey{}).(*http.Server); ok && hs != nil {
+			hs.Handler = fn
+			srvFunc = hs.Serve
+		}
 	}
 
-	go http.Serve(ts, fn)
+	if srvFunc != nil {
+		go srvFunc(ts)
+	} else {
+		go http.Serve(ts, fn)
+	}
 
 	go func() {
 		t := new(time.Ticker)

options.go

@@ -33,3 +33,9 @@ type middlewareKey struct{}
 func Middleware(mw ...func(http.Handler) http.Handler) server.Option {
 	return server.SetOption(middlewareKey{}, mw)
 }
+
+type serverKey struct{}
+
+func Server(hs *http.Server) server.Option {
+	return server.SetOption(serverKey{}, hs)
+}