diff --git a/v4.md b/v4.md
index 96c86884..09076c56 100644
--- a/v4.md
+++ b/v4.md
@@ -71,3 +71,11 @@ querier = querier.Commit()
 -- tx implements begin, commit, and rollback as save points
 -- conn implements begin as create tx (what about commit and rollback? No-op?)
 -- pool implements begin as?
+
+
+## Errors
+
+Consider Go error values proposal
+
+https://go.googlesource.com/proposal/+/master/design/go2draft-error-values-overview.md
+https://godoc.org/golang.org/x/xerrors