maps: enhance the robustness of the tests

Change-Id: I908e11196f55069d6dca6a19cd206629618e9f37
Reviewed-on: https://go-review.googlesource.com/c/go/+/496079
Auto-Submit: Keith Randall <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
Run-TryBot: xie cui <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

src/maps/maps_test.go

@@ -38,7 +38,7 @@ func TestKeys(t *testing.T) {
  var m = make(map[int]int)
  for i := 0; i < 840; i++ {
  want3 = append(want3, i)
- m[i] = i
+ m[i] = i * i
  }
 
  got3 := Keys(m)