_content/ref/mod: document go.work.sum files
There's no mention of go.work.sum files in ref/mod. Add some
mentioning when they can appear.
Fixes golang/go#51941
Change-Id: I377f6dcd0712ed8b9967469bc223543d784a6bd3
Reviewed-on: https://go-review.googlesource.com/c/website/+/563855
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
diff --git a/_content/ref/mod.md b/_content/ref/mod.md
index 9119c24..642b44d 100644
--- a/_content/ref/mod.md
+++ b/_content/ref/mod.md
@@ -1176,6 +1176,9 @@
[`golang.org/x/mod/modfile`](https://pkg.go.dev/golang.org/x/mod/modfile?tab=doc)
package can be used by Go programs to make the same changes programmatically.
+The go command will maintain a `go.work.sum` file that keeps track of hashes used by the workspace
+that are not in collective workspace modules' go.sum files.
+
### Lexical elements {#go-work-file-lexical}
Lexical elements in `go.work` files are defined in exactly the same way [as for
