1 files changed, 26 insertions, 0 deletions
diff --git a/vendor/github.com/pkg/errors/errors.go b/vendor/github.com/pkg/errors/errors.go
index a9840ecee..161aea258 100644
--- a/vendor/github.com/pkg/errors/errors.go
+++ b/vendor/github.com/pkg/errors/errors.go
@@ -260,3 +260,29 @@ func (w *withMessage) Format(s fmt.State, verb rune) {
 		io.WriteString(s, w.Error())
 	}
 }
+
+// Cause returns the underlying cause of the error, if possible.
+// An error value has a cause if it implements the following
+// interface:
+//
+//     type causer interface {
+//            Cause() error
+//     }
+//
+// If the error does not implement Cause, the original error will
+// be returned. If the error is nil, nil will be returned without further
+// investigation.
+func Cause(err error) error {
+	type causer interface {
+		Cause() error
+	}
+
+	for err != nil {
+		cause, ok := err.(causer)
+		if !ok {
+			break
+		}
+		err = cause.Cause()
+	}
+	return err
+}