code: func (a *Assertions) WithinDuration(expected time.Time, actual time.Time, delta time.Duration, msgAndArgs ...interface{}) {
  	if h, ok := a.t.(tHelper); ok {
  		h.Helper()
  	}
  	WithinDuration(a.t, expected, actual, delta, msgAndArgs...)
  }
docs: // WithinDuration asserts that the two times are within duration delta of each other.
  //
  //   a.WithinDuration(time.Now(), time.Now(), 10*time.Second)