use go1.11 with go mod

vendor/golang.org/x/sys/unix/race0.go

@@ -1,25 +0,0 @@
-// Copyright 2012 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 darwin,!race linux,!race freebsd,!race netbsd openbsd solaris dragonfly
-
-package unix
-
-import (
-	"unsafe"
-)
-
-const raceenabled = false
-
-func raceAcquire(addr unsafe.Pointer) {
-}
-
-func raceReleaseMerge(addr unsafe.Pointer) {
-}
-
-func raceReadRange(addr unsafe.Pointer, len int) {
-}
-
-func raceWriteRange(addr unsafe.Pointer, len int) {
-}