Race condition in fanout link

[osdrv]

WARNING: DATA RACE
Read at 0x00c0000f81c0 by goroutine 19:
  github.com/awesome-flow/flow/pkg/link/fanout.(*Fanout).fanout()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout.go:45 +0xaf
  github.com/awesome-flow/flow/pkg/link/fanout.New.func1()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout.go:32 +0x42

Previous write at 0x00c0000f81c0 by goroutine 17:
  github.com/awesome-flow/flow/pkg/link/fanout.(*Fanout).fanout()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout.go:52 +0x11d
  github.com/awesome-flow/flow/pkg/link/fanout.New.func1()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout.go:32 +0x42

Goroutine 19 (running) created at:
  github.com/awesome-flow/flow/pkg/link/fanout.New()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout.go:31 +0x1fe
  github.com/awesome-flow/flow/pkg/link/fanout.TestFanout_Send()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout_test.go:29 +0xdf
  testing.tRunner()
      /usr/local/Cellar/go/1.12.1/libexec/src/testing/testing.go:865 +0x163

Goroutine 17 (running) created at:
  github.com/awesome-flow/flow/pkg/link/fanout.New()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout.go:31 +0x1fe
  github.com/awesome-flow/flow/pkg/link/fanout.TestFanout_Send()
      /Users/olegs/workspace/golang/src/github.com/awesome-flow/flow/pkg/link/fanout/fanout_test.go:29 +0xdf
  testing.tRunner()
      /usr/local/Cellar/go/1.12.1/libexec/src/testing/testing.go:865 +0x163
==================
--- FAIL: TestFanout_Send (0.01s)