I ran depstubber using the following comment
//go:generate depstubber -vendor github.com/revel/revel Controller,Params
The stub generated for Params is wrong in several ways: the embedded field of type url.Values has been given the name Values; various methods, like Get, which are methods on url.Values have been created as methods on Params.
I have attached the generated stub. I had to change the extension to make that work.
stub.go.txt