feat: Add handlers (#133)

* feat: Support custom handlers when registering

You can add custom handlers (like BasicAuth used in the test) to /metrics.

* refactor: Nicer code to create handlers array

middleware.go

@@ -145,9 +145,11 @@ func NewWithLabels(labels map[string]string, namespace, subsystem string) *Fiber
 }
 
 // RegisterAt will register the prometheus handler at a given URL
-func (ps *FiberPrometheus) RegisterAt(app *fiber.App, url string) {
+func (ps *FiberPrometheus) RegisterAt(app *fiber.App, url string, handlers ...fiber.Handler) {
 	ps.defaultURL = url
-	app.Get(ps.defaultURL, adaptor.HTTPHandler(promhttp.Handler()))
+
+	h := append(handlers, adaptor.HTTPHandler(promhttp.Handler()))
+	app.Get(ps.defaultURL, h...)
 }
 
 // Middleware is the actual default middleware implementation

middleware_test.go

@@ -28,6 +28,7 @@ import (
 	"testing"
 
 	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/basicauth"
 )
 
 func TestMiddleware(t *testing.T) {
@@ -175,3 +176,38 @@ func TestMiddlewareWithLabels(t *testing.T) {
 		t.Errorf("got %s; want %s", got, want)
 	}
 }
+
+func TestMiddlewareWithBasicAuth(t *testing.T) {
+	app := fiber.New()
+
+	prometheus := New("basic-auth")
+	prometheus.RegisterAt(app, "/metrics", basicauth.New(basicauth.Config{
+		Users: map[string]string{
+			"prometheus": "password",
+		},
+	}))
+
+	app.Use(prometheus.Middleware)
+
+	app.Get("/", func(c *fiber.Ctx) error {
+		return c.SendString("Hello World")
+	})
+
+	req := httptest.NewRequest("GET", "/", nil)
+	resp, _ := app.Test(req, -1)
+	if resp.StatusCode != 200 {
+		t.Fail()
+	}
+
+	req = httptest.NewRequest("GET", "/metrics", nil)
+	resp, _ = app.Test(req, -1)
+	if resp.StatusCode != 401 {
+		t.Fail()
+	}
+
+	req.SetBasicAuth("prometheus", "password")
+	resp, _ = app.Test(req, -1)
+	if resp.StatusCode != 200 {
+		t.Fail()
+	}
+}