[alexfoo]

I wondered if you could sneak in some unicode digit but it seems to reject those too:

    $ go run z.go
    # command-line-arguments
    ./z.go:6:2: identifier cannot begin with digit U+0661 '١'
    ./z.go:7:27: identifier cannot begin with digit U+0661 '١'

(I tried a few of them but not all.)