This is due to the trailing Go! being parsed as a bang.
IIRC we've run into this before, one potential solution we thought of was to have a flag on each bang that would set whether it was allowed to be parsed as a trailing suffix bang (this is similar to what DDG has), but would take a lot of work and may not be the best solution. We could also just disallow "go!" specifically as it is pretty common to use.
