Add OpenTelemetry instrumentation with middleware-only approach

pkg/server/server.go

@@ -6,6 +6,7 @@ import (
 
 	"DanceLessonsCoach/pkg/config"
 	"DanceLessonsCoach/pkg/greet"
+	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"
 
 	"github.com/go-chi/chi/v5"
 	"github.com/go-chi/chi/v5/middleware"
@@ -13,14 +14,16 @@ import (
 )
 
 type Server struct {
-	router      *chi.Mux
-	readyCtx    context.Context
+	router   *chi.Mux
+	readyCtx context.Context
+	withOTEL bool
 }
 
 func NewServer(cfg *config.Config, readyCtx context.Context) *Server {
 	s := &Server{
-		router:    chi.NewRouter(),
-		readyCtx:  readyCtx,
+		router:   chi.NewRouter(),
+		readyCtx: readyCtx,
+		withOTEL: cfg.GetTelemetryEnabled(),
 	}
 	s.setupRoutes()
 	return s
@@ -41,7 +44,7 @@ func (s *Server) setupRoutes() {
 
 	// API routes
 	s.router.Route("/api/v1", func(r chi.Router) {
-		r.Use(s.apiMiddlewares()...)
+		r.Use(s.getAllMiddlewares()...)
 		s.registerApiV1Routes(r)
 	})
 }
@@ -54,11 +57,20 @@ func (s *Server) registerApiV1Routes(r chi.Router) {
 	})
 }
 
-func (s *Server) apiMiddlewares() []func(http.Handler) http.Handler {
-	return []func(http.Handler) http.Handler{
+// getAllMiddlewares returns all middleware including OpenTelemetry if enabled
+func (s *Server) getAllMiddlewares() []func(http.Handler) http.Handler {
+	middlewares := []func(http.Handler) http.Handler{
 		middleware.StripSlashes,
 		middleware.Recoverer,
 	}
+
+	if s.withOTEL {
+		middlewares = append(middlewares, func(next http.Handler) http.Handler {
+			return otelhttp.NewHandler(next, "")
+		})
+	}
+
+	return middlewares
 }
 
 func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
@@ -68,7 +80,7 @@ func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
 
 func (s *Server) handleReadiness(w http.ResponseWriter, r *http.Request) {
 	log.Info().Msg("Readiness check requested")
-	
+
 	select {
 	case <-s.readyCtx.Done():
 		log.Info().Msg("Readiness check: not ready (shutting down)")