Air carrier First Officer reported a critical ground conflict while on final approach resulting in a missed approach and declaration of minimum fuel.

Narrative

On final for Runway 8R tower cleared us to land and cleared an aircraft to cross the runway. Tower later told the aircraft to cancel crossing instructions and hold position. Aircraft Y informed tower the aircraft crossed the holding line. Tower told Aircraft Y to continue crossing; after which tower told us to go around. Tower cleared us to 7000ft and had us on a long vector. Captain inform tower we were close to min fuel; tower acknowledged; Captain later declared min fuel; tower acknowledge; however kept us on a vector away from the airport. Captain make additional call to Approach on our min fuel; they acknowledge with a promise to turn us in soon. We eventually got clearance and landed without incident.Suggestions: On our second approach Tower again cleared another aircraft to cross Runway 8R as we were again on final with a landing clearance. Considering the previous experience and not having enough fuel for a second go-around its concerning if the distance between the landing and crossing aircraft was appropriate. Also we should have been give the go around instruction prior to Aircraft Y instruction to continue crossing.