🔥 Feature: Add Skip middleware (#1465)

* add Skip middleware

* middleware/skip: fix test expectations

middleware/skip/README.md

@@ -0,0 +1,26 @@
+# Skip
+Skip middleware for [Fiber](https://github.com/gofiber/fiber) that skips a wrapped handler is a predicate is true.
+
+### Table of Contents
+- [Signatures](#signatures)
+- [Examples](#examples)
+
+
+### Signatures
+```go
+func New(handler fiber.Handler, exclude func(c *fiber.Ctx) bool) fiber.Handler
+```
+
+### Examples
+Import the middleware package that is part of the Fiber web framework
+```go
+import (
+  "github.com/gofiber/fiber/v2"
+  "github.com/gofiber/fiber/v2/middleware/skip"
+)
+```
+
+After you initiate your Fiber app, you can use the following possibilities:
+```go
+app.Use(skip.New(handler), func(ctx *fiber.Ctx) bool { return ctx.Method() == fiber.MethodOptions })
+```

middleware/skip/skip.go

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+package skip
+
+import "github.com/gofiber/fiber/v2"
+
+// New creates a middleware handler which skips the wrapped handler
+// if the exclude predicate returns true.
+func New(handler fiber.Handler, exclude func(c *fiber.Ctx) bool) fiber.Handler {
+	if exclude == nil {
+		return handler
+	}
+
+	return func(c *fiber.Ctx) error {
+		if exclude(c) {
+			return c.Next()
+		}
+
+		return handler(c)
+	}
+}

middleware/skip/skip_test.go

@@ -0,0 +1,54 @@
+package skip_test
+
+import (
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/gofiber/fiber/v2/middleware/skip"
+	"github.com/gofiber/fiber/v2/utils"
+)
+
+// go test -run Test_Skip
+func Test_Skip(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(skip.New(errTeapotHandler, func(*fiber.Ctx) bool { return true }))
+	app.Get("/", helloWorldHandler)
+
+	resp, err := app.Test(httptest.NewRequest("GET", "/", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, fiber.StatusOK, resp.StatusCode)
+}
+
+// go test -run Test_SkipFalse
+func Test_SkipFalse(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(skip.New(errTeapotHandler, func(*fiber.Ctx) bool { return false }))
+	app.Get("/", helloWorldHandler)
+
+	resp, err := app.Test(httptest.NewRequest("GET", "/", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, fiber.StatusTeapot, resp.StatusCode)
+}
+
+// go test -run Test_SkipNilFunc
+func Test_SkipNilFunc(t *testing.T) {
+	app := fiber.New()
+
+	app.Use(skip.New(errTeapotHandler, nil))
+	app.Get("/", helloWorldHandler)
+
+	resp, err := app.Test(httptest.NewRequest("GET", "/", nil))
+	utils.AssertEqual(t, nil, err)
+	utils.AssertEqual(t, fiber.StatusTeapot, resp.StatusCode)
+}
+
+func helloWorldHandler(c *fiber.Ctx) error {
+	return c.SendString("Hello, World 👋!")
+}
+
+func errTeapotHandler(*fiber.Ctx) error {
+	return fiber.ErrTeapot
+}