Air Traffic Control Fully Certified
Workload; Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach
Human Factors; Procedure
Aircraft X checked in and was immediately given a small S-turn for spacing between him and the preceding aircraft to be able to depart Aircraft Y. Everything appeared as though it would work. Aircraft Y was given an immediate takeoff clearance. As Aircraft X was in the flare; he initiated a go-around. Runway separation was close to 6000 feet and airborne but no action was taken by me because it seemed safer at that point to let the aircraft land rather than executing a go-around. It was simply a judgement call. Aircraft X was given a climb to 4000 feet and a 150 heading. I should have given Aircraft X a larger S turn or not tried to hit the gap with Aircraft X and Aircraft Y.
SAT Tower Controller reported an aircraft on short final initiated a go-around due to departing traffic from the same runway.