Dude, really sorry about this, it sucks balls. I quit commuting in my neck of woods for same reason, almost got mugged twice, one was arrested and had a knife on him. When a gang does this it is best just to hand over what they want, nothing you can do, guarantee one of them has a weapon and will kill. If you would have used that pepper spray it would have been fatal. I hope you get the bike back through insurance or pure luck by the police.