rca: investigate why TestRace didn't catch the data race in #1

[as]

No description provided.

[as]

It does detect the issue. I just didn't run the test.

==================
WARNING: DATA RACE
Write at 0x000000728720 by goroutine 14:
  crypto/cipher.fastXORBytes()
      /go/src/crypto/cipher/xor.go:34 +0x10a
  crypto/cipher.xorBytes()
      /go/src/crypto/cipher/xor.go:60 +0x9e
  crypto/cipher.(*cbcEncrypter).CryptBlocks()
      /go/src/crypto/cipher/cbc.go:72 +0x25a
  github.com/as/uuid.(*gen).V4()
      /g/src/github.com/as/uuid/uuid.go:68 +0x9e
  github.com/as/uuid.V4()
      /g/src/github.com/as/uuid/uuid.go:28 +0x9e
  github.com/as/uuid.TestRace.func1()
      /g/src/github.com/as/uuid/uuid_test.go:31 +0x66

Previous read at 0x000000728720 by goroutine 13:
  runtime.slicebytetostring()
      /go/src/runtime/string.go:75 +0x0
  github.com/as/uuid.V4()
      /g/src/github.com/as/uuid/uuid.go:30 +0xfd
  github.com/as/uuid.TestRace.func1()
      /g/src/github.com/as/uuid/uuid_test.go:31 +0x66

Goroutine 14 (running) created at:
  github.com/as/uuid.TestRace()
      /g/src/github.com/as/uuid/uuid_test.go:44 +0x107
  testing.tRunner()
      /go/src/testing/testing.go:827 +0x162

Goroutine 13 (running) created at:
  github.com/as/uuid.TestRace()
      /g/src/github.com/as/uuid/uuid_test.go:44 +0x107
  testing.tRunner()
      /go/src/testing/testing.go:827 +0x162