To adjust FOV (Field of View):

Within WillowInput.ini:

Search for [WillowGame.WillowPlayerInput]. Below the chunk of bindings, add the following:

Bindings=(Name="F10",Command="FOV 90",Control=False,Shift=False,Alt=False)
Bindings=(Name="F11",Command="FOV 110",Control=False,Shift=False,Alt=False)

You can change the keys (F10 and F11) to whatever you'd like, as well as the FOV values.

TIP: It's being reported that the FOV gets reset whenever you sprint in an online game. As a workaround, you can add the FOV command to one of your movement keys, like I have. Example - my MoveForward binding looks like this (my forward key is E):

Bindings=(Name="E",Command="MoveForward | Axis aGas Speed=+1.0 | FOV 96",Control=False,Shift=False,Alt=False,LeftTrigge r=False,RightTrigger=False,bIgnoreCtrl=False,bIgno reShift=False,bIgnoreAlt=False)