go.sum

@@ -3,6 +3,7 @@ github.com/golang-jwt/jwt/v4 v4.2.0/go.mod h1:/xlHOz8bRuivTWchD4jCa+NbatV+wEUSzw
 github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
 github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/imdario/mergo v0.3.12 h1:b6R2BslTbIEToALKP7LxUvijTsNI9TAe80pLWN2g/HU=
 github.com/imdario/mergo v0.3.12/go.mod h1:jmQim1M+e3UYxmgPu/WyfjB3N3VflVyUjjjwH0dnCYA=
 github.com/patrickmn/go-cache v2.1.0+incompatible h1:HRMgzkcYKYpi3C8ajMPV8OFXaaRUnok+kx1WdO15EQc=
 github.com/patrickmn/go-cache v2.1.0+incompatible/go.mod h1:3Qf8kWWT7OJRJbdiICTKqZju1ZixQ/KpMGzzAfe6+WQ=

handler.go

@@ -124,7 +124,12 @@ func (h *httpServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	if !match {
+	if !match && h.hd != nil {
+		if hdlr, ok := h.hd.Handler().(http.Handler); ok {
+			hdlr.ServeHTTP(w, r)
+			return
+		}
+	} else if !match {
 		h.errorHandler(ctx, nil, w, r, fmt.Errorf("not matching route found"), http.StatusNotFound)
 		return
 	}

http.go

@@ -22,6 +22,8 @@ import (
 	"golang.org/x/net/netutil"
 )
 
+var _ server.Server = &httpServer{}
+
 type httpServer struct {
 	hd           server.Handler
 	rsvc         *register.Service
@@ -448,12 +450,15 @@ func (h *httpServer) Start() error {
 		}
 	}
 
-	if handler == nil && h.hd == nil {
+	switch {
+	case handler == nil && h.hd == nil:
 		handler = h
-	} else if handler == nil && h.hd != nil {
+	case handler == nil && h.hd != nil:
 		if hdlr, ok := h.hd.Handler().(http.Handler); ok {
 			handler = hdlr
 		}
+	case len(h.handlers) > 0 && h.hd != nil:
+		handler = h
 	}
 
 	if handler == nil {
@@ -585,7 +590,7 @@ func (h *httpServer) Name() string {
 	return h.opts.Name
 }
 
-func NewServer(opts ...server.Option) server.Server {
+func NewServer(opts ...server.Option) *httpServer {
 	options := server.NewOptions(opts...)
 	return &httpServer{
 		opts:         options,