update godoc
diff --git a/errors.go b/errors.go
index 58996ba..0e4f94a 100644
--- a/errors.go
+++ b/errors.go
@@ -49,9 +49,13 @@
// invoked. This information can be retrieved with the following interface.
//
// type Stacktrace interface {
-// Stacktrace() []Frame
+// Stacktrace() errors.Stacktrace
// }
//
+// Where errors.Stacktrace is defined as
+//
+// type Stacktrace []Frame
+//
// The Frame type represents a call site in the stacktrace. Frame supports
// the fmt.Formatter interface that can be used for printing information about
// the stacktrace of this error. For example:
