Let's please use the standard one-liner formatting for this:

    func (vl VersionList) Len() int { return len(vl) }
    func (vl VersionList) Less(i, j int) bool { return vl[i].Less(vl[j]) }
    func (vl VersionList) Swap(i, j int) { vl[i], vl[j] = vl[j], vl[i] }