Air Carrier Flight Crew reported loss of ILS signal during approach to CLT in IMC.

Narrative

We were flying the ILS to Runway 18C at CLT and they had begun the process for turning the airport around to a north flow but we expected to be the last aircraft landing to the south. Passing the final approach fix (CYLOW) we could see on TCAS that the aircraft ahead of us had just landed on 18C. A few moments later we lost all approach guidance so we started to execute a go around since we were IMC at the time. We asked Tower if they were aware of the failure of the ILS signal and there was a long pause before they replied with instruction to go around if the Runway was not in sight. Following our go around we landed uneventfully to Runway 36L. I believe that in their rush to establish a north flow at CLT airport the controllers simply forgot we were on final with clearance for the south approach and lost track of us. I'm sure its already a policy to verify there are no aircraft on the approach before changing the active transmitters at the Field. Most likely the rush to change the airport flow led to the early navaid change and loss of guidance to our aircraft.