Key-values that should be deleted are not deleted from disk, even when Close() is called about badger HOT 5 CLOSED

fmt.Println("testBadger called")
opts := badger.DefaultOptions
dir := "/Users/stef/tmp"
opts.Dir = dir
opts.ValueDir = dir
b, err := badger.NewKV(&opts)
if err != nil {
    fmt.Println("error")
    return
}
key := []byte("key")
item := badger.KVItem{}
b.Get(key, &item)
if item.Value() == nil {
    fmt.Println("non existent key")
    val := []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789FOOBARZOGZOG")
    b.Set(key, val)
    fmt.Println("key value has been inserted")
    b.Get(key, &item)
    fmt.Println("getting the value")
    fmt.Println(string(item.Value()))
    b.Delete(key)
    fmt.Println("key value has been deleted")
    fmt.Println("getting the value again")
    b.Get(key, &item)
    fmt.Println(item.Value())
} else {
    fmt.Println("key exists")
    fmt.Println(string(item.Value()))
}
b.Close()