capnpc-go: fix bad string behavior in capnpc-go
capnpc-go: fix bad string behavior in capnpc-go

zombiezen/go-capnproto2,hodduc/go-capnproto2,zombiezen/go-capnproto,hodduc/go-capnproto2,zombiezen/go-capnproto2,zombiezen/go-capnproto