nits

storage/modules/block_storage.go

@@ -634,7 +634,8 @@ func (b *BlockStorage) SeeBlock(
 	ctx context.Context,
 	block *types.Block,
 ) error {
-	transaction := b.db.WriteTransaction(ctx, block.BlockIdentifier.Hash, true)
+	_, key := getBlockHashKey(block.BlockIdentifier.Hash)
+	transaction := b.db.WriteTransaction(ctx, string(key), true)
 	defer transaction.Discard(ctx)
 
 	// Store all transactions in order and check for duplicates

syncer/syncer.go

@@ -555,7 +555,14 @@ func (s *Syncer) syncRange(
 	s.concurrency = startingConcurrency
 	s.goalConcurrency = s.concurrency
 
-	// Spawn syncing goroutines
+	// We create a separate derivative context here instead of
+	// replacing the provided ctx because the context returned
+	// by errgroup.WithContext is canceled as soon as Wait returns.
+	// If this canceled context is passed to a handler or helper,
+	// it can have unintended consequences (some functions
+	// return immediately if the context is canceled).
+	//
+	// Source: https://godoc.org/golang.org/x/sync/errgroup
 	g, pipelineCtx := errgroup.WithContext(ctx)
 	g.Go(func() error {
 		return s.addBlockIndices(pipelineCtx, blockIndices, s.nextIndex, endIndex)