```keys := []int{3, 2, 8, 1}
sort.Ints(keys)
for i, j := 0, len(keys)-1; i < j; i, j = i+1, j-1 {
keys[i], keys[j] = keys[j], keys[i]
}
fmt.Println(keys)
```

This Go code sorts a slice of integers in descending order using the built-in sort.Ints function and a reverse iteration. Here’s how it works:

1. First, a slice of integers named keys is defined and initialized with the values {3, 2, 8, 1}.
2. Then, the sort.Ints function is called with keys as an argument. This function sorts the slice in ascending order.
3. After the sort function has been called, the slice keys will be in the order {1, 2, 3, 8}.
4. Next, a for loop is used to iterate over the slice in reverse order. The loop starts with i set to 0, j set to the length of the slice minus 1 (3 in this case), and the condition i < j. In each iteration, i is incremented by 1, and j is decremented by 1. 5. Inside the loop, the values at positions i and j in the slice are swapped using a multiple-assignment statement: keys[i], keys[j] = keys[j], keys[i]. This effectively reverses the order of the slice. 6. After the loop completes, the slice keys will be in the order {8, 3, 2, 1}. 7. Finally, the fmt.Println function is called with keys as an argument to print the contents of the slice to the console. The output will be [8 3 2 1].