Why can not use Pointer() method when reflect.Value is passed to an interface in golang?

I am writing a unit test to check equality of struct that contains func.

Here are my test code.
Go Palyround

When comparing, I used a func named GetFunctionName to get function's name for going.

func GetFunctionName(i interface{}) string {
	fmt.Printf("type in GetFunctionName: %v\n", reflect.TypeOf(reflect.ValueOf(i)))
	return runtime.FuncForPC(reflect.ValueOf(i).Pointer()).Name()
}

Also a compare function was made.

func SelectCompareStruct(got interface{}, want interface{}) {
	rvGot := reflect.ValueOf(got)
	rtGot := rvGot.Type()
	rvWant := reflect.ValueOf(want)
	rtWant := rvWant.Type()

	for i := 0; i < rtGot.NumField(); i++ {
		fieldGot := rtGot.Field(i)
		fieldWant := rtWant.Field(i)

		valueGot := rvGot.FieldByName(fieldGot.Name)
		valueWant := rvWant.FieldByName(fieldWant.Name)
		fmt.Printf("type in SelectCompareStruct: %v\n", reflect.TypeOf(reflect.ValueOf(valueGot)))

		// Works
		gotFuncNameInner := runtime.FuncForPC(valueGot.Pointer()).Name()
		wantFuncNameInner := runtime.FuncForPC(valueWant.Pointer()).Name()
		fmt.Printf("gotFuncNameInner:\n\t\t\t%v\nwantFuncNameInner:\n\t\t\t%v\n", gotFuncNameInner, wantFuncNameInner)

		// Does not work
		gotFuncName := GetFunctionName(valueGot)
		wantFuncName := GetFunctionName(valueWant)
		fmt.Printf("gotFuncName:\n\t%v\n wantFuncName:\n\t%v\n", gotFuncName, wantFuncName)
	}
}

You can see, when I write directly to get function's name, it works.
However, it does not work when using a func instead.
Although, both of which type that apply Pointer() method are reflect.Value type.

Yes, I can change input type of GetFunctionName to reflect.Value for working.
That's not good for other use cases. I want to make a function for getting name for versatility.
It will be beautiful to make input type interface{}.

Anyone have any idea why? And how to fix it?

The problem is that you are calling reflect.Value on a reflect.Value. Fix by removing the extra call to reflect.Value.

func GetFunctionName(v reflect.Value) string {
	fmt.Printf("type in GetFunctionName: %v\n", v.Type())
	return runtime.FuncForPC(v.Pointer()).Name()
}

Run it on the playground.