我应该如何在Go中定义一个空切片？

Or more precisely, it seems like I could do any of these three things. Is there any difference between them? Which is the best and why?

1. var foo []int
2. foo := []int{}
3. foo := make([]int, 0)

1) is a nil slice.

2) and 3) are non-nil slices with length zero and capacity zero.

Playground example

None of the options allocate memory.

All of the options are used commonly in Go code.

Because len, cap and append work with nil slices, 1) can often be used interchangeably with 2) and 3).