Tour of Go exercise #18: Slices, index out of range

I am working through the exercises in the Go tour and I have hit a snag that I can't figure out.

I'm doing Exercise: Slices and I am getting this error:

256 x 256

panic: runtime error: index out of range [0] with length 0

goroutine 1 [running]:
main.Pic(0x100, 0x100)
	/tmp/sandbox1628012103/prog.go:14 +0xcf
golang.org/x/tour/pic.Show(0xc0000001a0)
	/tmp/gopath962180923/pkg/mod/golang.org/x/tour@v0.0.0-20201207214521-004403599411/pic/pic.go:32 +0x28
main.main()
	/tmp/sandbox1628012103/prog.go:25 +0x25

Here is my code:

package main

import (
	"fmt"
	"golang.org/x/tour/pic"
)

func Pic(dx, dy int) [][]uint8 {
	fmt.Printf("%d x %d\n\n", dx, dy)

	pixels := make([][]uint8, 0, dy)

	for y := 0; y < dy; y++ {
		pixels[y] = make([]uint8, 0, dx)

		for x := 0; x < dx; x++ {
			pixels[y][x] = uint8(x * y)
		}
	}

	return pixels
}

func main() {
	pic.Show(Pic)
}

> Slices
>
> For a string, array, pointer to array, or slice a, the primary
> expression
>
> a[low : high]
>
> constructs a substring or slice. The index expressions low and high
> select which elements appear in the result. The result has indexes
> starting at 0 and length equal to high - low.
>
> For arrays or strings, the indexes low and high must satisfy 0 <= low
> <= high <= length; for slices, the upper bound is the capacity rather
> than the length.
>
> Indexes
>
> A primary expression of the form
>
> a[x]
>
> denotes the element of the array, slice, string or map a indexed by x.
> The value x is called the index or map key, respectively. The
> following rules apply:
>
> For a of type A or *A where A is an array type, or for a of type S
> where S is a slice type:
>
> x must be an integer value and 0 <= x < len(a)
>
> a[x] is the array element at index x and the type of a[x] is
> the element type of A
>
> if a is nil or if the index x is out of range, a run-time panic occurs
>
> Making slices, maps and channels
>
> make(T, n) slice slice of type T with length n and capacity n
> make(T, n, m) slice slice of type T with length n and capacity m
>

y must be an integer value and 0 <= y < len(pixel[]uint8). x must be an integer value and 0 <= x < len(pixel[][]uint8). For example,

package main

import "tour/pic"

func Pic(dx, dy int) [][]uint8 {
	pixels := make([][]uint8, dy)
	for y := 0; y < dy; y++ {
		pixels[y] = make([]uint8, dx)
		for x := 0; x < dx; x++ {
			pixels[y][x] = uint8(x * y)
		}
	}
	return pixels
}

func main() {
	pic.Show(Pic)
}

package main

import "tour/pic"

func Pic(dx, dy int) [][]uint8 {
fmt.Printf("%d x %d\n\n", dx, dy)

     pixels := make([][]uint8, 0, dy)

       for y := 0; y < dy; y++ {
    //    pixels[y] = make([]uint8, 0, dx)

for x := 0; x < dx; x++ {
 // append can skip make statement   
 pixels[y] = append(pixels[y],uint8(x*y)) 
  
     }
}

 return pixels
}

 func main() {
    pic.Show(Pic)
 }