time: add notes about monotonic time paused

See #66870

Change-Id: I781265355a3dbd0d9538bc9dcafaa83b482ec3f8
GitHub-Last-Rev: 9d92f11
GitHub-Pull-Request: #66922
Reviewed-on: https://go-review.googlesource.com/c/go/+/580515
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Joedian Reid <joedian@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/time/time.go

@@ -53,7 +53,10 @@
 //
 // On some systems the monotonic clock will stop if the computer goes to sleep.
 // On such a system, t.Sub(u) may not accurately reflect the actual
-// time that passed between t and u.
+// time that passed between t and u. The same applies to other functions and
+// methods that subtract times, such as [Since], [Until], [Before], [After],
+// [Add], [Sub], [Equal] and [Compare]. In some cases, you may need to strip
+// the monotonic clock to get accurate results.
 //
 // Because the monotonic clock reading has no meaning outside
 // the current process, the serialized forms generated by t.GobEncode,