There is no published missed approach for a visual approach in IFR, so technically you should ask ATC. However you can reasonably be expected to fly the missed approach of the original instrument approach.
If not given, when performing a visual approach, it is the responsibility of the crew to request missed approach instructions in the event of a missed approach.
There are airports with precision and non precision approaches for the same runway, but containing different missed approach procedures. That said, Missed approach procedures as published on instrument approach charts are applicable to those procedures only, unless otherwise instructed by ATC.