impossible to install on Linux

- Linux 5.3.0-53-generic #47~18.04.1-Ubuntu SMP Thu May 7 13:10:50 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
- go version go1.14.2 linux/amd64

I've installed libgtk-3-dev, andlabs/ui.

```
$ go get github.com/andlabs/wakeup
# github.com/andlabs/wakeup
../../go/src/github.com/andlabs/wakeup/main.go:46:11: undefined: ui.LineEdit
../../go/src/github.com/andlabs/wakeup/main.go:47:11: undefined: ui.LineEdit
../../go/src/github.com/andlabs/wakeup/main.go:61:4: undefined: ui.Post
../../go/src/github.com/andlabs/wakeup/main.go:77:10: mw.win.MsgBoxError undefined (type *ui.Window has no field or method MsgBoxError)
../../go/src/github.com/andlabs/wakeup/main.go:83:10: mw.win.MsgBoxError undefined (type *ui.Window has no field or method MsgBoxError)
../../go/src/github.com/andlabs/wakeup/main.go:100:23: not enough arguments in call to ui.NewWindow
have (string, number, number)
want (string, int, int, bool)
../../go/src/github.com/andlabs/wakeup/main.go:101:8: mw.win.Closing undefined (type *ui.Window has no field or method Closing)
../../go/src/github.com/andlabs/wakeup/main.go:102:8: mw.win.Posted undefined (type *ui.Window has no field or method Posted)
../../go/src/github.com/andlabs/wakeup/main.go:103:14: undefined: ui.NewLineEdit
../../go/src/github.com/andlabs/wakeup/main.go:104:15: undefined: ui.NewLineEdit
../../go/src/github.com/andlabs/wakeup/main.go:104:15: too many errors
```