Engine failure at flaps 30...increase thrust on good engine to maintain your speed...if not possible,retract to flaps 15 and add 15kts(-700s) and 20 kts(800-900s).
All 737s except maybe the 200s will have enough thrust to maintain speed at high gross weight and high field temperature.
---->In case of a go around ,retract to flaps 15.
Warning:you must know your aircraft max weight to achieve the missed approach climb gradient.(Flaps 15,TOGA on remaining engine).It is a dispatch requirement just as a max landing weight/runway landing distance would be).
If you decide to retract to Flaps 15 and then have to Goaround,use normal single engine procedure.
Hope that helps.