Or if a flashlight would cause a problem, you can use a laser pointer, at least to help focus. I picked up a cheap (<$20 on ebay) green laser pointer (easier to see and brighter at lower power) with front lens attachments that split the beam into assorted shapes. I use the grid shape mostly, but if you're trying not to disturb the subject much, there was one that just spreads the beam out to maybe 2-3 inches wide by the time it's 10-15 feet out. That can give you a good basis for autofocus (especially with the grid shape)… focus with that, then set it to manual and turn the laser off.
If you're trying wildlife photography, you might want to look at using a laser or sound trigger:
https://www.facebook.com/HSFTRIGGERS https://triggertrap.com
You can set up a laser trigger near a salt lick to catch deer, or a bird feeder or nesting site to catch birds. The HSF-triggers guy puts his micro triggers on sale dirt cheap sometimes (I got a set on Black Friday for 90% off and my wife bought me a second set plus the very handy delay box for 70% off), and since the trigger cable is basically an audio mono cable, you can add additional length to it very inexpensively, and with the right adapter you can use it to fire off the flash instead of the camera (not that big a deal for a deer, but much easier to freeze a hummingbird or a water balloon popping).