Package fsutil builds on the underlying fs to add useful functions such as WriteFile or Walk.

Chroot wraps a Filesystem interface modifying paths in order to constrain them to a specific directory.

OS is a wrapper around os package.

Spread wraps a filesystem and spreads files in directories accordin to their name in order not to have a single folder with millions of subdirectories.

FS is the main interface that abstracts the os package functions that operate on files.