NewLoop create new loop instance.

WalkFS walks the file tree rooted at root, calling walkFn for each file or directory in the tree, including root.

ChanSize is default channel size.

StepClose is close step id.

Chans contains channels and mutex for loop.

Consumer is object represent single loop consumer task.

Loop is a loop on a filespace.

LoopData is loop data container.

Producer produce data for loop.

WalkFunc is Walk callback.