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