Creating a channel asynchronously - race detector testing

race_test.go

package gorace // run with go test -race

import (
        "sync"
        "testing"
        "time"
)

var (
        every = 100 * time.Millisecond
        after = 150 * time.Millisecond
        delay = 200 * time.Millisecond
)

func TestSafe_mutex(t *testing.T) {
        tick := time.Tick(every)

        var mu sync.Mutex
        var tock <-chan time.Time
        getTock := func() <-chan time.Time {
                mu.Lock()
                defer mu.Unlock()
                return tock
        }

        go func() {
                time.Sleep(after)
                mu.Lock()
                defer mu.Unlock()
                tock = time.Tick(delay)
        }()

        for i := 0; i < 10; i++ {
                select {
                case <-tick:
                        t.Logf("Tick %s\n", time.Now())
                case <-getTock():
                        t.Logf("Tock %s\n", time.Now())
                }
        }
}

func TestSafe_channel(t *testing.T) {
        tick := time.Tick(every)

        tockReady := make(chan (<-chan time.Time))
        go func() {
                time.Sleep(after)
                tockReady <- time.Tick(delay)
        }()

        var tock <-chan time.Time
        for i := 0; i < 10; i++ {
                select {
                case tock = <-tockReady:
                        t.Logf("Tock ready\n")
                case <-tick:
                        t.Logf("Tick %s\n", time.Now())
                case <-tock:
                        t.Logf("Tock %s\n", time.Now())
                }
        }

}

func TestRace_var(t *testing.T) {
        tick := time.Tick(every)

        var mu sync.Mutex
        var tock <-chan time.Time

        go func() {
                time.Sleep(after)
                mu.Lock()
                tock = time.Tick(delay)
        }()

        for i := 0; i < 10; i++ {
                select {
                case <-tick:
                        t.Logf("Tick %s\n", time.Now())
                case <-tock:
                        t.Logf("Tock %s\n", time.Now())
                }
        }
}

func TestRace_ptr(t *testing.T) {
        tick := time.Tick(every)

        var mu sync.Mutex
        var tock <-chan time.Time

        p := &tock
        go func() {
                time.Sleep(after)
                mu.Lock()
                *p = time.Tick(delay)
        }()

        for i := 0; i < 10; i++ {
                select {
                case <-tick:
                        t.Logf("Tick %s\n", time.Now())
                case <-*p:
                        t.Logf("Tock %s\n", time.Now())
                }
        }
}

zz_output

==================
WARNING: DATA RACE
Write at 0x00c000010020 by goroutine 14:
  _/tmp/gorace.TestRace_var.func1()
      /tmp/gorace/race_test.go:75 +0x8e

Previous read at 0x00c000010020 by goroutine 13:
  _/tmp/gorace.TestRace_var()
      /tmp/gorace/race_test.go:82 +0x189
  testing.tRunner()
      /usr/lib/google-golang/src/testing/testing.go:865 +0x163

Goroutine 14 (running) created at:
  _/tmp/gorace.TestRace_var()
      /tmp/gorace/race_test.go:72 +0x102
  testing.tRunner()
      /usr/lib/google-golang/src/testing/testing.go:865 +0x163

Goroutine 13 (running) created at:
  testing.(*T).Run()
      /usr/lib/google-golang/src/testing/testing.go:916 +0x699
  testing.runTests.func1()
      /usr/lib/google-golang/src/testing/testing.go:1159 +0xa8
  testing.tRunner()
      /usr/lib/google-golang/src/testing/testing.go:865 +0x163
  testing.runTests()
      /usr/lib/google-golang/src/testing/testing.go:1157 +0x523
  testing.(*M).Run()
      /usr/lib/google-golang/src/testing/testing.go:1074 +0x2eb
  main.main()
      _testmain.go:48 +0x222
==================
--- FAIL: TestRace_var (0.75s)
    race_test.go:81: Tick 2019-04-11 13:21:29.965519506 -0700 PDT m=+1.553782437
    race_test.go:81: Tick 2019-04-11 13:21:30.065483846 -0700 PDT m=+1.653746663
    race_test.go:81: Tick 2019-04-11 13:21:30.165504594 -0700 PDT m=+1.753767529
    race_test.go:83: Tock 2019-04-11 13:21:30.215938983 -0700 PDT m=+1.804201852
    race_test.go:81: Tick 2019-04-11 13:21:30.265532886 -0700 PDT m=+1.853795820
    race_test.go:81: Tick 2019-04-11 13:21:30.365505412 -0700 PDT m=+1.953768348
    race_test.go:83: Tock 2019-04-11 13:21:30.415963429 -0700 PDT m=+2.004226365
    race_test.go:81: Tick 2019-04-11 13:21:30.465525752 -0700 PDT m=+2.053788687
    race_test.go:81: Tick 2019-04-11 13:21:30.565490398 -0700 PDT m=+2.153753342
    race_test.go:83: Tock 2019-04-11 13:21:30.615941258 -0700 PDT m=+2.204204207
    testing.go:809: race detected during execution of test
==================
WARNING: DATA RACE
Write at 0x00c000114028 by goroutine 16:
  _/tmp/gorace.TestRace_ptr.func1()
      /tmp/gorace/race_test.go:98 +0x90

Previous read at 0x00c000114028 by goroutine 15:
  _/tmp/gorace.TestRace_ptr()
      /tmp/gorace/race_test.go:105 +0x12c
  testing.tRunner()
      /usr/lib/google-golang/src/testing/testing.go:865 +0x163

Goroutine 16 (running) created at:
  _/tmp/gorace.TestRace_ptr()
      /tmp/gorace/race_test.go:95 +0x102
  testing.tRunner()
      /usr/lib/google-golang/src/testing/testing.go:865 +0x163

Goroutine 15 (running) created at:
  testing.(*T).Run()
      /usr/lib/google-golang/src/testing/testing.go:916 +0x699
  testing.runTests.func1()
      /usr/lib/google-golang/src/testing/testing.go:1159 +0xa8
  testing.tRunner()
      /usr/lib/google-golang/src/testing/testing.go:865 +0x163
  testing.runTests()
      /usr/lib/google-golang/src/testing/testing.go:1157 +0x523
  testing.(*M).Run()
      /usr/lib/google-golang/src/testing/testing.go:1074 +0x2eb
  main.main()
      _testmain.go:48 +0x222
==================
--- FAIL: TestRace_ptr (0.75s)
    race_test.go:104: Tick 2019-04-11 13:21:30.716809242 -0700 PDT m=+2.305072176
    race_test.go:104: Tick 2019-04-11 13:21:30.816801624 -0700 PDT m=+2.405064563
    race_test.go:104: Tick 2019-04-11 13:21:30.916805626 -0700 PDT m=+2.505068565
    race_test.go:106: Tock 2019-04-11 13:21:30.967261682 -0700 PDT m=+2.555524617
    race_test.go:104: Tick 2019-04-11 13:21:31.016773655 -0700 PDT m=+2.605036620
    race_test.go:104: Tick 2019-04-11 13:21:31.116817055 -0700 PDT m=+2.705079938
    race_test.go:106: Tock 2019-04-11 13:21:31.167264561 -0700 PDT m=+2.755527493
    race_test.go:104: Tick 2019-04-11 13:21:31.216804368 -0700 PDT m=+2.805067304
    race_test.go:104: Tick 2019-04-11 13:21:31.316801462 -0700 PDT m=+2.905064397
    race_test.go:106: Tock 2019-04-11 13:21:31.367269934 -0700 PDT m=+2.955532845
    testing.go:809: race detected during execution of test
FAIL
exit status 1
FAIL    _/tmp/gorace    2.995s