You would still be going the speed of light. When you are inside a container, like a train, your speed is the same as the container while it is moving, it doesn’t change if you start moving around inside.
Charlie, James is right, it’s a weird thing about relativity, if you walk to the front of a train an observer would see you as travelling at the speed of atrain plus your speed. and by your logic based on the inside of a train your travelling at walking speed, but if oyu look outside your faster than the train. PROBLEM is with speed of light, it’s relative so light would still be travelling the speed of light in the train and outside, it all depends on the observer and frame of reference.