diff --git a/demo_test/vendor/golang.org/x/sys/unix/sockcmsg_unix_other.go b/demo_test/vendor/golang.org/x/sys/unix/sockcmsg_unix_other.go
new file mode 100644
index 0000000..7d08dae
--- /dev/null
+++ b/demo_test/vendor/golang.org/x/sys/unix/sockcmsg_unix_other.go
@@ -0,0 +1,38 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build aix darwin freebsd linux netbsd openbsd solaris
+
+package unix
+
+import (
+	"runtime"
+)
+
+// Round the length of a raw sockaddr up to align it properly.
+func cmsgAlignOf(salen int) int {
+	salign := SizeofPtr
+
+	// dragonfly needs to check ABI version at runtime, see cmsgAlignOf in
+	// sockcmsg_dragonfly.go
+	switch runtime.GOOS {
+	case "aix":
+		// There is no alignment on AIX.
+		salign = 1
+	case "darwin", "illumos", "solaris":
+		// NOTE: It seems like 64-bit Darwin, Illumos and Solaris
+		// kernels still require 32-bit aligned access to network
+		// subsystem.
+		if SizeofPtr == 8 {
+			salign = 4
+		}
+	case "netbsd", "openbsd":
+		// NetBSD and OpenBSD armv7 require 64-bit alignment.
+		if runtime.GOARCH == "arm" {
+			salign = 8
+		}
+	}
+
+	return (salen + salign - 1) & ^(salign - 1)
+}