From aeb7619109b3442c7570a2c0bc030e4079e586dd Mon Sep 17 00:00:00 2001
From: Kurnia D Win <kurnia.d.win@gmail.com>
Date: Wed, 15 Jan 2020 15:07:21 +0700
Subject: [PATCH] fix Cause

Some error struct have `Cause() error` method indicating the cause of
the error, but that method could return nil indicating that that itself
is the root cause in the error chain

look at this struct
```go
type myError struct {
  message string
  cause   error
}

func (m *myError) Error() string { ... }

func (m *myError) Cause() error {
  return m.cause
}

func New(message string) error {
  return &myError{message: message}
}
```
---
 errors.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/errors.go b/errors.go
index 161aea2..bc93026 100644
--- a/errors.go
+++ b/errors.go
@@ -282,7 +282,11 @@ func Cause(err error) error {
 		if !ok {
 			break
 		}
-		err = cause.Cause()
+		if cerr := cause.Cause(); cerr != nil {
+			err = cerr
+		} else {
+			break
+		}
 	}
 	return err
 }