Data race

[Skarlso]

Got to look at this later on:

=== RUN   TestGetWorkServer
==================
WARNING: DATA RACE
Write at 0x0000018cdea0 by goroutine 50:
  github.com/gaia-pipeline/gaia/workers/server.TestGetWorkServer()
      /go/src/github.com/gaia-pipeline/gaia/workers/server/worker_test.go:140 +0xf8
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:909 +0x199

Previous read at 0x0000018cdea0 by goroutine 48:
  [failed to restore the stack]

Goroutine 50 (running) created at:
  testing.(*T).Run()
      /usr/local/go/src/testing/testing.go:960 +0x651
  testing.runTests.func1()
      /usr/local/go/src/testing/testing.go:1202 +0xa6
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:909 +0x199
  testing.runTests()
      /usr/local/go/src/testing/testing.go:1200 +0x521
  testing.(*M).Run()
      /usr/local/go/src/testing/testing.go:1117 +0x2ff
  main.main()
      _testmain.go:110 +0x337

Goroutine 48 (running) created at:
  github.com/gaia-pipeline/gaia/workers/server.TestStart()
      /go/src/github.com/gaia-pipeline/gaia/workers/server/server_test.go:41 +0x4f1
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:909 +0x199
==================