how to scale a cameras FOV in real time.

i am creating a fps camera, and when the player sprints i want the FOV to smoothly scale from 80 to 90. I tried using Mathf.Lerp(80,90,Time.time); but that just caused it to instantly pop from 80 to 90, if i use deltaTime the fov will only go from 80 to 91, if anyone has a solution to this i would be very happy to hear it.

float moved = 0;

void Update ()
    moved += Time.DeltaTime * scalingFactor;

then just check for moved being >= 1

the value moved has to be between 0 and 1. time.deltatime will be the same every time and Time.time is > 1 so will go straight to the target value