Regarding your second question, my guess is that it is rather unlikely to get this into the standard library.
First, AFAIK the stdlib is maintained by the core Go team and they are surely very cautious about extending the stdlb with more and more and more functionality.
Second, CR2 is one of many image formats. (It is also a proprietary format by Canon.) When adding support for CR2, requests for supporting more image formats will follow. And there are really many of them - just have a look at the file types that ExifTool supports.
I’d say just write your own CR2 package and publish it on GitHub or elsewhere, and add it to godoc.org. Anyone who searches for CR2 libraries surely will find it. Whether or not it is part of the stdlib is maybe not as important.