Addition of Locals Function with Go Generics as an Alternative to c.Locals

ctx.go

@@ -817,6 +817,21 @@ func (c *DefaultCtx) Locals(key any, value ...any) any {
 	return value[0]
 }
 
+// Locals function utilizing Go's generics feature.
+// This function allows for manipulating and retrieving local values within a request context with a more specific data type.
+func Locals[V any](c Ctx, key any, value ...any) V {
+	ctx, ok := c.(*DefaultCtx)
+	if !ok {
+		panic(fmt.Errorf("failed to type-assert to *DefaultCtx"))
+	}
+	var v V
+	v, ok = ctx.Locals(key, value...).(V)
+	if !ok {
+		panic(fmt.Errorf("failed to type-assert to %T", v))
+	}
+	return v
+}
+
 // Location sets the response Location HTTP header to the specified path parameter.
 func (c *DefaultCtx) Location(path string) {
 	c.setCanonical(HeaderLocation, path)

ctx_test.go

@@ -1757,6 +1757,50 @@ func Test_Ctx_Locals(t *testing.T) {
 	require.Equal(t, StatusOK, resp.StatusCode, "Status code")
 }
 
+// go test -run Test_Ctx_Locals_Generic
+func Test_Ctx_Locals_Generic(t *testing.T) {
+	t.Parallel()
+	app := New()
+	app.Use(func(c Ctx) error {
+		Locals[string](c, "john", "doe")
+		Locals[int](c, "age", 18)
+		Locals[bool](c, "isHuman", true)
+		return c.Next()
+	})
+	app.Get("/test", func(c Ctx) error {
+		require.Equal(t, "doe", Locals[string](c, "john"))
+		require.Equal(t, 18, Locals[int](c, "age"))
+		require.Equal(t, true, Locals[bool](c, "isHuman"))
+		return nil
+	})
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/test", nil))
+	require.NoError(t, err, "app.Test(req)")
+	require.Equal(t, StatusOK, resp.StatusCode, "Status code")
+}
+
+// go test -run Test_Ctx_Locals_GenericCustomStruct
+func Test_Ctx_Locals_GenericCustomStruct(t *testing.T) {
+	t.Parallel()
+
+	type User struct {
+		name string
+		age  int
+	}
+
+	app := New()
+	app.Use(func(c Ctx) error {
+		Locals[User](c, "user", User{"john", 18})
+		return c.Next()
+	})
+	app.Use("/test", func(c Ctx) error {
+		require.Equal(t, User{"john", 18}, Locals[User](c, "user"))
+		return nil
+	})
+	resp, err := app.Test(httptest.NewRequest(MethodGet, "/test", nil))
+	require.NoError(t, err, "app.Test(req)")
+	require.Equal(t, StatusOK, resp.StatusCode, "Status code")
+}
+
 // go test -run Test_Ctx_Method
 func Test_Ctx_Method(t *testing.T) {
 	t.Parallel()

docs/api/ctx.md

@@ -1000,6 +1000,34 @@ app.Get("/admin", func(c fiber.Ctx) error {
 })
 ```
 
+An alternative version of the Locals method that takes advantage of Go's generics feature is also available. This version 
+allows for the manipulation and retrieval of local values within a request's context with a more specific data type.
+
+```go title="Signature"
+func Locals[V any](c Ctx, key any, value ...any) V
+```
+
+```go title="Example"
+app.Use(func(c Ctx) error {
+    fiber.Locals[string](c, "john", "doe")
+    fiber.Locals[int](c, "age", 18)
+    fiber.Locals[bool](c, "isHuman", true)
+    return c.Next()
+})
+app.Get("/test", func(c Ctx) error {
+	fiber.Locals[string](c, "john")     // "doe"
+    fiber.Locals[int](c, "age")         // 18
+    fiber.Locals[bool](c, "isHuman")    // true
+return nil
+})
+````
+
+Keep in mind, you will need Go 1.18 or later to take advantage of generics. Also, be aware of the types you pass into 
+the generic function. A runtime panic will occur if the type does not match the expected type.
+
+Make sure to understand and correctly implement the Locals method in both its standard and generic form for better control 
+over route-specific data within your application.
+
 ## Location
 
 Sets the response [Location](https://developer.mozilla.org/ru/docs/Web/HTTP/Headers/Location) HTTP header to the specified path parameter.