Add docs from gofiber/fiber@2db1858

docs/core/middleware/keyauth.md

@@ -214,14 +214,15 @@ curl --header "Authorization: Bearer my-super-secret-key"  http://localhost:3000
 
 ## Config
 
-| Property       | Type                                     | Description                                                                                            | Default                       |
-|:---------------|:-----------------------------------------|:-------------------------------------------------------------------------------------------------------|:------------------------------|
-| Next           | `func(fiber.Ctx) bool`                  | Next defines a function to skip this middleware when returned true.                                    | `nil`                         |
-| SuccessHandler | `fiber.Handler`                          | SuccessHandler defines a function which is executed for a valid key.                                   | `nil`                         |
-| ErrorHandler   | `fiber.ErrorHandler`                     | ErrorHandler defines a function which is executed for an invalid key.                                  | `401 Invalid or expired key`  |
-| KeyLookup      | `string`                                 | KeyLookup is a string in the form of "`<source>:<name>`" that is used to extract key from the request. | "header:Authorization"        |
-| AuthScheme     | `string`                                 | AuthScheme to be used in the Authorization header.                                                     | "Bearer"                      |
-| Validator      | `func(fiber.Ctx, string) (bool, error)` | Validator is a function to validate the key.                                                           | A function for key validation |
+| Property        | Type                                     | Description                                                                                            | Default                       |
+|:----------------|:-----------------------------------------|:-------------------------------------------------------------------------------------------------------|:------------------------------|
+| Next            | `func(fiber.Ctx) bool`                   | Next defines a function to skip this middleware when returned true.                                    | `nil`                         |
+| SuccessHandler  | `fiber.Handler`                          | SuccessHandler defines a function which is executed for a valid key.                                   | `nil`                         |
+| ErrorHandler    | `fiber.ErrorHandler`                     | ErrorHandler defines a function which is executed for an invalid key.                                  | `401 Invalid or expired key`  |
+| KeyLookup       | `string`                                 | KeyLookup is a string in the form of "`<source>:<name>`" that is used to extract the key from the request. | "header:Authorization"        |
+| CustomKeyLookup | `KeyLookupFunc` aka `func(c fiber.Ctx) (string, error)` | If more complex logic is required to extract the key from the request, an arbitrary function to extract it can be specified here. Utility helper functions are described below. |  `nil` |
+| AuthScheme      | `string`                                 | AuthScheme to be used in the Authorization header.                                                     | "Bearer"                      |
+| Validator       | `func(fiber.Ctx, string) (bool, error)`  | Validator is a function to validate the key.                                                           | A function for key validation |
 
 ## Default Config
 
@@ -237,6 +238,13 @@ var ConfigDefault = Config{
 		return c.Status(fiber.StatusUnauthorized).SendString("Invalid or expired API Key")
 	},
 	KeyLookup:  "header:" + fiber.HeaderAuthorization,
+	CustomKeyLookup: nil,
 	AuthScheme: "Bearer",
 }
 ```
+
+## CustomKeyLookup
+
+Two public utility functions are provided that may be useful when creating custom extraction:
+* `DefaultKeyLookup(keyLookup string, authScheme string)`: This is the function that implements the default `KeyLookup` behavior, exposed to be used as a component of custom parsing logic
+* `MultipleKeySourceLookup(keyLookups []string, authScheme string)`: Creates a CustomKeyLookup function that checks each listed source using the above function until a key is found or the options are all exhausted. For example, `MultipleKeySourceLookup([]string{"header:Authorization", "header:x-api-key", "cookie:apikey"}, "Bearer")` would first check the standard Authorization header, checks the `x-api-key` header next, and finally checks for a cookie named `apikey`. If any of these contain a valid API key, the request continues. Otherwise, an error is returned.