Spied method panics when not returning anything

[MikeWarren2014]

Upon testing a method that takes a callback function, to do some async operation, I use your library to create a spy:

type MySpy struct {
    *spies.Spy
}

func (my *MySpy) Callback(res CallResultSt, data interface{}) {
    my.Called(res, data)
    fmt.Println("Hello world")
    return
}

The method under test has an implementation like this (although this is extremely simplified):

go func(data interface{}) { 
    callback(apiCore.SendRequest([data here]), data)
}(callbackCustomData)

Immediately after calling the method that does that, I say :

spy.MatchMethod("Callback", spies.AnyArgs, "")

When I run the test, I get greeted with

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
    panic: runtime error: invalid memory address or nil pointer dereference

Somehow, it fails to find the callback that I just defined for it!

There's no good documentation on how to remedy this. The callback taken by the method under test isn't supposed to return anything (we're doing async stuff).

[MikeWarren2014]

UPDATE: I made that spies.Spy the object, not the dereference of a pointer. It now works, as in it doesn't panic, but now it throws error upon testing asynchronous function.