title: Error in Go's slices exercise
body: <p>I'm trying to solve the slices exercise. My current solution is</p>
  
  <pre><code>package main
  
  import "golang.org/x/tour/pic"
  
  func Pic(dx, dy int) [][]uint8 {
      picture := make([][]uint8, dy)
  
      x := dx
  
      for iy := 0; iy &lt; dy; iy++ {
          picture[iy] = make([]uint8, dx)
  
          for ix := 0; ix &lt; dx; ix++ {
              x = (x+dy)/2
              picture[iy][ix] = uint8(x)
          }
      }
  
      return picture
  }
  
  func main() {
      pic.Show(Pic(1,2))
  }
  </code></pre>
  
  <p>But I'm getting the following error</p>
  
  <blockquote>
    <p>tmp/sandbox931798243/main.go:23: cannot use Pic(1, 2) (type [][]uint8)
    as type func(int, int) [][]uint8 in argument to pic.Show</p>
  </blockquote>
  
  <p>What am I doing wrong? Might that be a bug with the sandbox?</p>