GrowSlice
Use append to show how the capacity of a slice grows.func TestSlice(t *testing.T) {
s := make([]int, 0)
last := cap(s)
max := 20
for i := 0; i < max; i++ {
s = append(s, i)
if cap(s) != last {
t.Logf("len(s)=%v cap(s)=%v\n", len(s), cap(s))
last = cap(s)
}
}
exp := max
if cap(s) != exp {
t.Fail()
}
}