nil is a valid slice

nil is a valid slice of length 0. This means that,

• You should not return a slice of length zero explicitly. Return nil instead.

  Bad	Good
  ```go if x == "" { return []int{} } ```	```go if x == "" { return nil } ```

• To check if a slice is empty, always use len(s) == 0. Do not check for nil.

  Bad	Good
  ```go func isEmpty(s []string) bool { return s == nil } ```	```go func isEmpty(s []string) bool { return len(s) == 0 } ```

• The zero value (a slice declared with var) is usable immediately without make().

  Bad	Good
  ```go nums := []int{} // or, nums := make([]int) if add1 { nums = append(nums, 1) } if add2 { nums = append(nums, 2) } ```	```go var nums []int if add1 { nums = append(nums, 1) } if add2 { nums = append(nums, 2) } ```

Remember that, while it is a valid slice, a nil slice is not equivalent to an allocated slice of length 0 - one is nil and the other is not - and the two may be treated differently in different situations (such as serialization).