Not making slice copies correctly
The builtin copy function allows copying elements from one slice to another.
Mistake
The number of elements copied to the destination slice corresponds to the minimum value between the source slice length and the destination slice length. If the destination slice is an empty slice, then 0 elements will be copied.
Fix
Use a destination slice with a length equal to or greater than the source slice
src := []int{0, 1, 2}
dest := make([]int, len(src))
copy(dest, src)
The alternative append form which is more concise, but less obvious
src := []int{0, 1, 2}
dest := append([]int(nil), src...)