Potential race condition in SinkIndex

[KyleMaas]

(Trying to keep track of some of the things I'm finding so I can remember to look at them later.)

This section should probably be wrapped in a mutex:

margaret/indexes/sinkindex.go

Lines 42 to 49 in 22ed48a

	err := idx.f(ctx, tv.Seq(), tv.Value(), idx.idx)
	if err != nil {
	return fmt.Errorf("error calling setter func: %w", err)
	}
	err = idx.idx.SetSeq(tv.Seq())
	if err != nil {
	return fmt.Errorf("error setting sequence number: %w", err)
	}