fixed broken Docker build.
fixed broken Docker build.

segmentio/gddo,segmentio/gddo,segmentio/gddo,sourcegraph/gddo,sourcegraph/gddo,golang/gddo,sourcegraph/gddo,jeweljar/gddo,golang/gddo,jeweljar/gddo,segmentio/gddo,jeweljar/gddo,golang/gddo,jeweljar/gddo,sourcegraph/gddo,golang/gddo