use go1.11 with go mod

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

@@ -1,30 +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
-
-package unix
-
-import (
-	"runtime"
-	"unsafe"
-)
-
-const raceenabled = true
-
-func raceAcquire(addr unsafe.Pointer) {
-	runtime.RaceAcquire(addr)
-}
-
-func raceReleaseMerge(addr unsafe.Pointer) {
-	runtime.RaceReleaseMerge(addr)
-}
-
-func raceReadRange(addr unsafe.Pointer, len int) {
-	runtime.RaceReadRange(addr, len)
-}
-
-func raceWriteRange(addr unsafe.Pointer, len int) {
-	runtime.RaceWriteRange(addr, len)
-}