Update gomod and vendor

vendor/github.com/docker/go-events/errors.go

@@ -0,0 +1,10 @@
+package events
+
+import "fmt"
+
+var (
+	// ErrSinkClosed is returned if a write is issued to a sink that has been
+	// closed. If encountered, the error should be considered terminal and
+	// retries will not be successful.
+	ErrSinkClosed = fmt.Errorf("events: sink closed")
+)