resolve: to prevent goroutine leak, make certain to cancel the contex…

…t involved in running the source used to resolve start block.

pipeline/resolve.go

@@ -212,7 +212,10 @@ func resolveStartBlockNum(ctx context.Context, req *pbsubstreamsrpc.Request, res
 		return 0, "", nil, connect.NewError(connect.CodeInvalidArgument, fmt.Errorf("StartCursor is invalid: LIB %d greater than Block %d", cursor.LIB.Num(), cursor.Block.Num()))
 	}
 
-	reorgJunctionBlock, head, err := resolveCursor(ctx, cursor)
+	resolveCtx, resolveCancel := context.WithCancel(ctx)
+	defer resolveCancel()
+
+	reorgJunctionBlock, head, err := resolveCursor(resolveCtx, cursor)
 	if err != nil {
 		return 0, "", nil, connect.NewError(connect.CodeInvalidArgument, fmt.Errorf("cannot resolve StartCursor %q: %s", cursor, err.Error()))
 	}