🔥 feat: Add End() method to Ctx (#3280)

* 🔥 Feature(v3): Add End() method to Ctx

* 🎨 Style(Ctx): Respect linter in tests

* 🚨 Test(End): Add timeout test for c.End()

* 📚 Doc: Update End() documentation examples to use 4 spaces

* 🚨 Test: Update `c.End()` tests to use StatusOK

---------

Co-authored-by: Giovanni Rivera <grivera64@users.noreply.github.com>
Co-authored-by: Juan Calderon-Perez <835733+gaby@users.noreply.github.com>

ctx.go

@@ -1986,3 +1986,20 @@ func (c *DefaultCtx) Drop() error {
 	//nolint:wrapcheck // error wrapping is avoided to keep the operation lightweight and focused on connection closure.
 	return c.RequestCtx().Conn().Close()
 }
+
+// End immediately flushes the current response and closes the underlying connection.
+func (c *DefaultCtx) End() error {
+	ctx := c.RequestCtx()
+	conn := ctx.Conn()
+
+	bw := bufio.NewWriter(conn)
+	if err := ctx.Response.Write(bw); err != nil {
+		return err
+	}
+
+	if err := bw.Flush(); err != nil {
+		return err //nolint:wrapcheck // unnecessary to wrap it
+	}
+
+	return conn.Close() //nolint:wrapcheck // unnecessary to wrap it
+}

ctx_test.go

@@ -5931,6 +5931,83 @@ func Test_Ctx_DropWithMiddleware(t *testing.T) {
 	require.Nil(t, resp)
 }
 
+// go test -run Test_Ctx_End
+func Test_Ctx_End(t *testing.T) {
+	app := New()
+
+	app.Get("/", func(c Ctx) error {
+		c.SendString("Hello, World!") //nolint:errcheck // unnecessary to check error
+		return c.End()
+	})
+
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/", nil))
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+	require.Equal(t, StatusOK, resp.StatusCode)
+	body, err := io.ReadAll(resp.Body)
+	require.NoError(t, err, "io.ReadAll(resp.Body)")
+	require.Equal(t, "Hello, World!", string(body))
+}
+
+// go test -run Test_Ctx_End_after_timeout
+func Test_Ctx_End_after_timeout(t *testing.T) {
+	app := New()
+
+	// Early flushing handler
+	app.Get("/", func(c Ctx) error {
+		time.Sleep(2 * time.Second)
+		return c.End()
+	})
+
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/", nil))
+	require.ErrorIs(t, err, os.ErrDeadlineExceeded)
+	require.Nil(t, resp)
+}
+
+// go test -run Test_Ctx_End_with_drop_middleware
+func Test_Ctx_End_with_drop_middleware(t *testing.T) {
+	app := New()
+
+	// Middleware that will drop connections
+	// that persist after c.Next()
+	app.Use(func(c Ctx) error {
+		c.Next() //nolint:errcheck // unnecessary to check error
+		return c.Drop()
+	})
+
+	// Early flushing handler
+	app.Get("/", func(c Ctx) error {
+		c.SendStatus(StatusOK) //nolint:errcheck // unnecessary to check error
+		return c.End()
+	})
+
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/", nil))
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+	require.Equal(t, StatusOK, resp.StatusCode)
+}
+
+// go test -run Test_Ctx_End_after_drop
+func Test_Ctx_End_after_drop(t *testing.T) {
+	app := New()
+
+	// Middleware that ends the request
+	// after c.Next()
+	app.Use(func(c Ctx) error {
+		c.Next() //nolint:errcheck // unnecessary to check error
+		return c.End()
+	})
+
+	// Early flushing handler
+	app.Get("/", func(c Ctx) error {
+		return c.Drop()
+	})
+
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/", nil))
+	require.ErrorIs(t, err, ErrTestGotEmptyResponse)
+	require.Nil(t, resp)
+}
+
 // go test -run Test_GenericParseTypeString
 func Test_GenericParseTypeString(t *testing.T) {
 	t.Parallel()

docs/api/ctx.md

@@ -484,6 +484,54 @@ app.Get("/", func(c fiber.Ctx) error {
 })
 ```
 
+## End
+
+End immediately flushes the current response and closes the underlying connection.
+
+```go title="Signature"
+func (c fiber.Ctx) End() error
+```
+
+```go title="Example"
+app.Get("/", func(c fiber.Ctx) error {
+    c.SendString("Hello World!")
+    return c.End()
+})
+```
+
+:::caution
+Calling `c.End()` will disallow further writes to the underlying connection.
+:::
+
+End can be used to stop a middleware from modifying a response of a handler/other middleware down the method chain
+when they regain control after calling `c.Next()`.
+
+```go title="Example"
+// Error Logging/Responding middleware
+app.Use(func(c fiber.Ctx) error {
+    err := c.Next()
+
+    // Log errors & write the error to the response
+    if err != nil {
+        log.Printf("Got error in middleware: %v", err)
+        return c.Writef("(got error %v)", err)
+    }
+
+    // No errors occured
+    return nil
+})
+
+// Handler with simulated error
+app.Get("/", func(c fiber.Ctx) error {
+    // Closes the connection instantly after writing from this handler
+    // and disallow further modification of its response
+    defer c.End()
+
+    c.SendString("Hello, ... I forgot what comes next!")
+    return errors.New("some error")
+})
+```
+
 ## Format
 
 Performs content-negotiation on the [Accept](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Accept) HTTP header. It uses [Accepts](ctx.md#accepts) to select a proper format from the supplied offers. A default handler can be provided by setting the `MediaType` to `"default"`. If no offers match and no default is provided, a 406 (Not Acceptable) response is sent. The Content-Type is automatically set when a handler is selected.

docs/whats_new.md

@@ -341,6 +341,7 @@ testConfig := fiber.TestConfig{
 - **String**: Similar to Express.js, converts a value to a string.
 - **ViewBind**: Binds data to a view, replacing the old `Bind` method.
 - **CBOR**: Introducing [CBOR](https://cbor.io/) binary encoding format for both request & response body. CBOR is a binary data serialization format which is both compact and efficient, making it ideal for use in web applications.
+- **End**: Similar to Express.js, immediately flushes the current response and closes the underlying connection.
 
 ### Removed Methods
 
@@ -403,6 +404,41 @@ app.Get("/sse", func(c fiber.Ctx) {
 
 You can find more details about this feature in [/docs/api/ctx.md](./api/ctx.md).
 
+### End
+
+In v3, we introduced a new method to match the Express.js API's `res.end()` method.
+
+```go
+func (c Ctx) End()
+```
+
+With this method, you can:
+
+- Stop middleware from controlling the connection after a handler further up the method chain
+  by immediately flushing the current response and closing the connection.
+- Use `return c.End()` as an alternative to `return nil`
+
+```go
+app.Use(func (c fiber.Ctx) error {
+    err := c.Next()
+    if err != nil {
+        log.Println("Got error: %v", err)
+        return c.SendString(err.Error()) // Will be unsuccessful since the response ended below
+    }
+    return nil
+})
+
+app.Get("/hello", func (c fiber.Ctx) error {
+    query := c.Query("name", "")
+    if query == "" {
+        c.SendString("You don't have a name?")
+        c.End() // Closes the underlying connection
+        return errors.New("No name provided")
+    }
+    return c.SendString("Hello, " + query + "!")
+})
+```
+
 ---
 
 ## 🌎 Client package