go iterator ergonomics improvement

[wkalt]

It would be nice to introduce some kind of More() style convenience like in the rosbag reader example here: https://github.com/foxglove/go-rosbag#reading-a-bag-file

I think this can probably be done backward compatibly with the existing calling style, which is to break out of the loop on EOF. If using More-style, the EOF-producing call would not be made.

Let me know if it seems desirable and I may raise a patch.

[defunctzombie]

Is this More convention something other file readers in golang do? My initial impression (coming from what we do in typescript) is that .Next() returns stuff to read or an indication that there's no more stuff to read so we typically iterate on next and avoid the sort of "double call" to query if there is more and then read more.

I do think have a More (or I've seen it called Peek in other apis) is useful on its own even when its still nice to use next to do the iteration.