Cloud Datastore（Raceで失敗するようなやつ）

hoge.go

// Raceで失敗するようなやつ
func TestExampleDataStore3(t *testing.T) {
  testWithAEInstance(t, true, func(inst *aetest.Instance) {
    req, err := (*inst).NewRequest("GET", "/", nil)
    require.Nil(t, err)

    ctx := appengine.NewContext(req)

    // 1. Point入れる
    stringID := "this_is_point_key"
    now := time.Now()
    p := point.Point{
      ID:        stringID,
      UserID:    "1",
      ExpiredAt: now,
      IsUsed:    false,
      CreatedAt: now,
      UpdatedAt: now,
    }

    // Put
    k := datastore.NewKey(ctx, "Point", stringID, 0, nil)
    _, err = datastore.Put(ctx, k, &p)
    require.Nil(t, err)

    done := make(chan error)
    go func() {
      // 2. goroutineで、PointをGetして、2秒待って、PointをPutする
      err2outer := datastore.RunInTransaction(ctx, func(tx netcontext.Context) error {
        p2 := point.Point{}
        datastore.Get(tx, k, &p2)
        fmt.Println("==(in groutine)== Show p2")
        fmt.Println(p2)

        time.Sleep(2 * time.Second)

        p2.IsUsed = true

        _, err2 := datastore.Put(tx, k, &p2)
        if err2 != nil {
          return err2
        }

        return nil
      }, &datastore.TransactionOptions{Attempts: 1})
      done <- err2outer
    }()

    // 3. 1秒待って、PointをGetして、PointをPutする
    err3outer := datastore.RunInTransaction(ctx, func(tx netcontext.Context) error {
      time.Sleep(1 * time.Second)

      p3 := point.Point{}
      datastore.Get(tx, k, &p3)
      fmt.Println("== Show p3")
      fmt.Println(p3)

      p3.IsUsed = true

      _, err3 := datastore.Put(tx, k, &p3)
      if err3 != nil {
        return err3
      }

      return nil
    }, &datastore.TransactionOptions{Attempts: 1})

    // 3.は成功し、2.は失敗する
    fmt.Println("== err3")
    fmt.Println(err3outer)

    select {
    case err := <-done:
      fmt.Println("== err2")
      fmt.Println(err)
      return
    }
  })
}
// =>
// % go test ./src/****/test/... -v --run TestExampleDataStore3
// === RUN   TestExampleDataStore3
// WARNING  2017-12-13 08:04:04,081 application_configuration.py:167] The Managed VMs runtime is deprecated, please consider migrating your application to use the Flexible runtime. See https://cloud.google.com/appengine/docs/flexible/python/migrating for more details.
// INFO     2017-12-13 08:04:04,081 devappserver2.py:105] Skipping SDK update check.
// WARNING  2017-12-13 08:04:04,082 devappserver2.py:121] DEFAULT_VERSION_HOSTNAME will not be set correctly with --port=0
// WARNING  2017-12-13 08:04:04,136 simple_search_stub.py:1174] Could not read search indexes from /var/folders/qx/58dtxr9j4mv6k26s0x49w0whzmn1qb/T/appengine.testapp.katsunori.kawaguchi/search_indexes
// INFO     2017-12-13 08:04:04,139 api_server.py:300] Starting API server at: http://localhost:64041
// INFO     2017-12-13 08:04:05,740 dispatcher.py:251] Starting module "default" running at: http://localhost:64042
// INFO     2017-12-13 08:04:05,743 admin_server.py:116] Starting admin server at: http://localhost:64046
// ==(in groutine)== Show p2
// { 1 2017-12-13 08:04:05.743314 +0000 UTC false 2017-12-13 08:04:05.743314 +0000 UTC 2017-12-13 08:04:05.743314 +0000 UTC}
// == Show p3
// { 1 2017-12-13 08:04:05.743314 +0000 UTC false 2017-12-13 08:04:05.743314 +0000 UTC 2017-12-13 08:04:05.743314 +0000 UTC}
// == err3
// <nil>
// == err2
// datastore: concurrent transaction
// --- PASS: TestExampleDataStore3 (7.37s)
// PASS
// ok      github.com/****/****/src/****/test        7.391s