TestGetDieCh() strange behaviour seems cause by racing

[cs8425]

run test with: go test -coverprofile=coverage.txt -covermode=atomic -v -run=TestGetDieCh .

in session_test.go:

func TestGetDieCh(t *testing.T) {
	cs, ss, err := getSmuxStreamPair()
	if err != nil {
		t.Fatal(err)
	}
	defer ss.Close()
	dieCh := ss.GetDieCh()
	go func() {
		t.Log("start")
		select {
		case <-dieCh:
		case <-time.Tick(time.Second):
			t.Fatal("wait die chan timeout")
		}
		t.Log("end")
	}()
	cs.Close()
	t.Log("wait")
}

will got:

=== RUN   TestGetDieCh
    session_test.go:298: start
    session_test.go:307: wait
--- PASS: TestGetDieCh (0.00s)
PASS
coverage: 32.5% of statements
ok  	github.com/xtaci/smux	0.004s	coverage: 32.5% of statements

and

=== RUN   TestGetDieCh
    session_test.go:307: wait
--- PASS: TestGetDieCh (0.00s)
PASS
panic: Log in goroutine after TestGetDieCh has completed: end


goroutine 27 [running]:
testing.(*common).logDepth(0xc000121380, {0xc00021c030, 0x4}, 0x3)
	/usr/local/go/src/testing/testing.go:779 +0x4c9
testing.(*common).log(...)
	/usr/local/go/src/testing/testing.go:761
testing.(*common).Log(0xc000215fb0, {0xc000215fa0, 0x0, 0x0})
	/usr/local/go/src/testing/testing.go:800 +0x45
github.com/xtaci/smux.TestGetDieCh.func1()
	/path-to-code/smux/session_test.go:304 +0x11f
created by github.com/xtaci/smux.TestGetDieCh
	/path-to-code/smux/session_test.go:297 +0x112
FAIL	github.com/xtaci/smux	0.006s
FAIL

if we change to this, be sure that test exit after goroutine:

func TestGetDieCh(t *testing.T) {
	cs, ss, err := getSmuxStreamPair()
	if err != nil {
		t.Fatal(err)
	}
	defer ss.Close()
	dieCh := ss.GetDieCh()

	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()

		t.Log("start")
		select {
		case <-dieCh:
			t.Log("end")
		case <-time.Tick(time.Second):
			t.Fatal("wait die chan timeout")
		}
	}()
	cs.Close()

	t.Log("wait...")
	wg.Wait()
}

the test will fail with:

=== RUN   TestGetDieCh
    session_test.go:313: wait...
    session_test.go:303: start
    session_test.go:308: wait die chan timeout
--- FAIL: TestGetDieCh (1.00s)
FAIL
coverage: 32.5% of statements
FAIL	github.com/xtaci/smux	1.005s
FAIL