type reflection of pointer to struct in go

I'm having problems determine the type of a struct when I only have a pointer to the struct.

type TypeA struct {
  Foo string
}

type TypeB struct {
  Bar string
}

I have to implement the following callback:

func Callback(param interface{}) {

}

param can be *TypeA or *TypeB.

How can I determine the Type of param?

reflect.TypeOf(param) seems not to work with a pointer.

When I do this

func Callback(param interface{}) {
  n := reflect.TypeOf(param).Name()
  fmt.Printf(n)
}

The output is empty

Thanks in advance for any help.