What they're suggesting is that `time.Duration` should not be an int64.

  1 second * 1 second = 1 second²
  1 meter * 1 meter = 1 meter²
  1 meter / 1 second = 1 m/s

Those are not user errors, those are physical values. A physical value is two things:

  - a scalar (int64, float, ...)
  - a unit (meter, second, inches, ...)

If the type system of your programming language does not allow you to define units, this should at least be a structure with a scalar and an enum, and functions to cast from one unit to another (if possible).

Working with units is a common thing in science.