typ := &TYP{InternalState: "filled"}
setNil(typ)

fmt.Printf("Expecting that %v to be nil", typ)

func setNilIf(v *interface{}) {
    *v = nil
}

var i interface{} = "Bob"
fmt.Printf("Before: %vn", i)
setNilIf(&i)
fmt.Printf("After: %vn", i)

Before: Bob
After: <nil>

func setNilPtr(p unsafe.Pointer) {
    *(**int)(p) = nil
}

typ := &TYP{InternalState: "filled"}
fmt.Printf("Before: %vn", typ)
setNilPtr(unsafe.Pointer(&typ))
fmt.Printf("After: %vn", typ)

Before: &{filled}
After: <nil>

func setNilPtr2(i interface{}) {
    v := reflect.ValueOf(i)
    v.Elem().Set(reflect.Zero(v.Elem().Type()))
}

typ2 := &TYP{InternalState: "filled"}
fmt.Printf("Before: %vn", typ2)
setNilPtr2(&typ2)
fmt.Printf("After: %vn", typ2)

Before: &{filled}
After: <nil>

i = nil
typ = nil