Update go.mod fixing issue "invalid pseudo-version: does not match version-control timestamp" (#229)
Update go.mod fixing issue "invalid pseudo-version: does not match version-control timestamp" (#229)

Issue when built with Go v1.13:
github.com/BurntSushi/xgb@v0.0.0-20160522221800-27f122750802: invalid pseudo-version: does not match version-control timestamp (2016-05-22T18:18:43Z)
go-vgo/robotgo,go-vgo/robotgo,go-vgo/robotgo