Include package name in Setup function.

Writing-Middleware.md

@@ -54,7 +54,7 @@ In your package, create a `Setup` function which will be used to set up your mid
 
 ```go
 // Setup configures a new MyHandler middleware instance.
-func Setup(c *Controller) (middleware.Middleware, error) {
+func Setup(c *setup.Controller) (middleware.Middleware, error) {
 	for c.Next() {
 		// do parsing
 	}