Update README.md
Update README's example so cancelFn is only called if it's set
@@ -469,7 +469,9 @@ response.
}
// Ensure the context is canceled to prevent leaking.
// See context package for more information, https://golang.org/pkg/context/
+ if cancelFn {
defer cancelFn()
+ }
// Uploads the object to S3. The Context will interrupt the request if the
// timeout expires.
