```go
package main

import (
"fmt"
"reflect"
)

type arrT struct {
Arr []int
}

func main() {
tt := arrT{
Arr: []int{1, 2},
}

arrValue := reflect.ValueOf(&tt).Elem().FieldByName("Arr")
fmt.Printf("%v, %T\n", arrValue, arrValue)

arrValue.Set(reflect.Append(arrValue, reflect.ValueOf(80)))
// panic: reflect: call of reflect.Value.Elem on slice Value

fmt.Println("Slice after appending data:", tt)
}
```