1.42 seems to be having some problems with Go 1.18 (see #2649), so let's
just upgrade to latest. There was one new error, suggesting to use `%q`
rather than `"%s"`, since the former does escapes properly. It doesn't
really matter for us -- the string should be an identifier -- but it
doesn't hurt. (Plus it wanted us to upgrade from ioutil, which I did
in #181.)
Test plan: make check