I actually made something like this a long time ago using command blocks, but now that datapacks are a thing, I decided to remake it, and even better than it was before!

Once the main station is generated, it will generate a new section of a railway bridge once you reach the end of it, and continue to do so until you have gone to the border of the world.

To generate the main station that creates the whole thing, simply click the command in the book called "Build Infinite Railway" and where you stand is where the station will generate.

Simply do /reload to get the build manual.