I have two Xcodes in my mac :
Xcode 10.1 : I can run all the apps in simulators and doesn't give any problems
Xcode 10.3 : I can run the apps on real devices but while running on simulators they stuck on apple logo
I have tried restarting the Xcode & mac, but still it didn't help me.
While the simulator is stuck at apple logo, Xcode displays launching "app name".
UnInstalling Xcode 10.3 and Re-Installing of Xcode resolved the issue.