package main import ( "fmt" "reflect" ) func main() { var x uint64 = 42 v := reflect.ValueOf(&x).Elem() v.SetUint(100) fmt.Println(x) // prints 100 }In this example, we create an unsigned 64-bit integer variable `x` with the value 42. We then create a reflect.Value struct for a pointer to `x` using `reflect.ValueOf(&x)`. We call `Elem()` to get the reflect.Value for `x` itself. Finally, we call the `SetUint` method on the reflect.Value to change the value of `x` to 100. The package library for this code sample is "reflect".