v[0:10] is wrongly highlighted as goOctalError

[MoZhonghua]

What did you do? (required: The issue will be closed when not provided)

vim-go wrongly highlight v[0:10] as goOctalError, mininal example:

func f() {
  v := make([]int, 0)
  _ = v[0:10]
}

What did you expect to happen?

No highlight for "0:10"

What happened instead?

vim-go wrongly highlight v[0:10] as goOctalError, like this:

vim-go version:

master@de681fd117