Bad use of package global causes data race, clobbered chunkers #4
Description
Hi! Thanks for this implementation!
I noticed that while it looks like NewChunker returns a new chunker based on the given options, it actually depends on the global table variable, meaning two chunkers with different seed values will stomp on each other, and chunkers cannot be constructed concurrently without causing a data race.
WARNING: DATA RACE
Read at 0x00000594c720 by goroutine 163:
github.com/jotfs/fastcdc-go.NewChunker()
/Users/jb/go/pkg/mod/github.com/jotfs/[email protected]/fastcdc.go:110 +0x124
...
Previous write at 0x00000594c720 by goroutine 206:
github.com/jotfs/fastcdc-go.NewChunker()
/Users/jb/go/pkg/mod/github.com/jotfs/[email protected]/fastcdc.go:110 +0x155
...