diff --git a/unum/vendor/golang.org/x/net/internal/socket/error_windows.go b/unum/vendor/golang.org/x/net/internal/socket/error_windows.go
new file mode 100644
index 0000000..6a6379a
--- /dev/null
+++ b/unum/vendor/golang.org/x/net/internal/socket/error_windows.go
@@ -0,0 +1,26 @@
+// Copyright 2017 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.
+
+package socket
+
+import "syscall"
+
+var (
+	errERROR_IO_PENDING error = syscall.ERROR_IO_PENDING
+	errEINVAL           error = syscall.EINVAL
+)
+
+// errnoErr returns common boxed Errno values, to prevent allocations
+// at runtime.
+func errnoErr(errno syscall.Errno) error {
+	switch errno {
+	case 0:
+		return nil
+	case syscall.ERROR_IO_PENDING:
+		return errERROR_IO_PENDING
+	case syscall.EINVAL:
+		return errEINVAL
+	}
+	return errno
+}