Included in iOS’s Control Center is access to a flashlight. Once enabled, you can quickly shut it off by using the flashlight shortcut from the lock screen.

Optionally 

• “Hey Siri, tun off the flashlight”
  
  
• Swipe down from the upper right corner of your Home or Lock screen and tap the flashlight icon.
  
  
• Activate the Lock screen by raising to wake or pressing the Side button, and press the flashlight icon.