initial prometheus metrics support, simplfied some code

internal/server/instance.go

@@ -1,25 +0,0 @@
-package server
-
-var proxyServer, apiServer *Server
-
-func InitProxyServer(opt Options) *Server {
-	if proxyServer == nil {
-		proxyServer = NewServer(opt)
-	}
-	return proxyServer
-}
-
-func InitAPIServer(opt Options) *Server {
-	if apiServer == nil {
-		apiServer = NewServer(opt)
-	}
-	return apiServer
-}
-
-func GetProxyServer() *Server {
-	return proxyServer
-}
-
-func GetAPIServer() *Server {
-	return apiServer
-}

internal/server/server.go

@@ -38,6 +38,12 @@ type Options struct {
 	Handler         http.Handler
 }
 
+func StartServer(opt Options) (s *Server) {
+	s = NewServer(opt)
+	s.Start()
+	return s
+}
+
 func NewServer(opt Options) (s *Server) {
 	var httpSer, httpsSer *http.Server
 	var httpHandler http.Handler