🆕 add expvar middleware

It's wrapper of fasthttp/expvarhandler

middleware/expvar/README.md

@@ -0,0 +1,61 @@
+# Expvar
+Expvar middleware for [Fiber](https://github.com/gofiber/fiber) that serves via its HTTP server runtime profiling data in the format expected by the expvar visualization tool. The package is typically only imported for the side effect of registering its HTTP handlers. The handled paths all begin with /debug/expvar/.
+
+- [Signatures](#signatures)
+- [Examples](#example)
+
+### Signatures
+```go
+func New() fiber.Handler
+```
+
+### Example
+Import the expvar package that is part of the Fiber web framework
+
+```go
+package main
+
+import (
+	"expvar"
+	"fmt"
+
+	"github.com/gofiber/fiber/v2"
+	expvarmw "github.com/gofiber/fiber/v2/middleware/expvar"
+)
+
+var count = expvar.NewInt("count")
+
+func main() {
+	app := fiber.New()
+	app.Use(expvarmw.New())
+	app.Get("/", func(c *fiber.Ctx) error {
+		count.Add(1)
+
+		return c.SendString(fmt.Sprintf("hello expvar count %d", count.Value()))
+	})
+
+	fmt.Println(app.Listen(":3000"))
+}
+```
+
+Visit path `/debug/vars` to see all vars and use query `r=key` to filter exposed variables.
+
+```bash
+curl 127.0.0.1:3000
+hello expvar count 1
+
+curl 127.0.0.1:3000/debug/vars
+{
+	"cmdline": ["xxx"],
+	"count": 1,
+	"expvarHandlerCalls": 33,
+	"expvarRegexpErrors": 0,
+	"memstats": {...}
+}
+
+curl 127.0.0.1:3000/debug/vars?r=c
+{
+	"cmdline": ["xxx"],
+	"count": 1
+}
+```

middleware/expvar/expvar.go

@@ -0,0 +1,26 @@
+package expvar
+
+import (
+	"strings"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/valyala/fasthttp/expvarhandler"
+)
+
+// New creates a new middleware handler
+func New() fiber.Handler {
+	// Return new handler
+	return func(c *fiber.Ctx) error {
+		path := c.Path()
+		// We are only interested in /debug/vars routes
+		if len(path) < 11 || !strings.HasPrefix(path, "/debug/vars") {
+			return c.Next()
+		}
+		if path == "/debug/vars" {
+			expvarhandler.ExpvarHandler(c.Context())
+			return nil
+		}
+
+		return c.Redirect("/debug/vars", 302)
+	}
+}

middleware/expvar/expvar_test.go

@@ -0,0 +1,83 @@
+package expvar
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/utils"
+)
+
+func Test_Non_Expvar_Path(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(New())
+
+	app.Get("/", func(c *fiber.Ctx) error {
+		return c.SendString("escaped")
+	})
+
+	resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, 200, resp.StatusCode)
+
+	b, err := ioutil.ReadAll(resp.Body)
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, "escaped", string(b))
+}
+
+func Test_Expvar_Index(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(New())
+
+	app.Get("/", func(c *fiber.Ctx) error {
+		return c.SendString("escaped")
+	})
+
+	resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/debug/vars", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, 200, resp.StatusCode)
+	utils.AssertEqual(t, fiber.MIMEApplicationJSONCharsetUTF8, resp.Header.Get(fiber.HeaderContentType))
+
+	b, err := ioutil.ReadAll(resp.Body)
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, true, bytes.Contains(b, []byte("cmdline")))
+	utils.AssertEqual(t, true, bytes.Contains(b, []byte("memstat")))
+}
+
+func Test_Expvar_Filter(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(New())
+
+	app.Get("/", func(c *fiber.Ctx) error {
+		return c.SendString("escaped")
+	})
+
+	resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/debug/vars?r=cmd", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, 200, resp.StatusCode)
+	utils.AssertEqual(t, fiber.MIMEApplicationJSONCharsetUTF8, resp.Header.Get(fiber.HeaderContentType))
+
+	b, err := ioutil.ReadAll(resp.Body)
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, true, bytes.Contains(b, []byte("cmdline")))
+	utils.AssertEqual(t, false, bytes.Contains(b, []byte("memstat")))
+}
+
+func Test_Expvar_Other_Path(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(New())
+
+	app.Get("/", func(c *fiber.Ctx) error {
+		return c.SendString("escaped")
+	})
+
+	resp, err := app.Test(httptest.NewRequest(fiber.MethodGet, "/debug/vars/302", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, 302, resp.StatusCode)
+}