According to the theory of relativity in physics, it is impossible for an object with mass to travel at the speed of light. As an object with mass approaches the speed of light, its relativistic mass increases, requiring an infinite amount of energy to reach that speed.
However, if we were to consider a hypothetical scenario where you could travel at the speed of light, time dilation would occur. From the perspective of an observer on Earth, time would appear to slow down for you as you approach the speed of light.
From your perspective, however, time would appear to pass normally. This means that, if you were able to travel at the speed of light, you would perceive the journey of one light year to be instantaneous.
Keep in mind that this hypothetical scenario assumes the laws of physics as we currently understand them. In reality, it is not currently possible for objects with mass to reach or exceed the speed of light.