net: TestTCPServer/tcp4_:0<-127.0.0.1 failures on Windows with EOF (and no other output)

[bcmills]

--- FAIL: TestTCPServer (0.02s)
    --- FAIL: TestTCPServer/tcp4_:0<-127.0.0.1 (0.00s)
        server_test.go:113: #19: EOF
FAIL
FAIL	net	54.788s

greplogs -l -e 'FAIL: TestTCPServer .*(?:\n[ ]+.*)* EOF'
2022-05-13T21:00:31-e755a56/windows-amd64-longtest
2019-11-07T02:33:31-198f045/windows-amd64-longtest

Probably a good first step would be to update this test to log more information about what's going on (per https://go.dev/wiki/CodeReviewComments#useful-test-failures), although given the low rate of occurrence it may be a while before we get another hit. 😅

(CC @ianlancetaylor @neild @golang/windows)

[ZekeLu]

I have tried to modify transceiver() to write hard-coded error into the channel. According to my test, the EOF error can only appear on line 308 and send to the channel on line 313. It seems that there is not more information can be added to the test to help diagnose this issue.

go/src/net/mockserver_test.go

Lines 289 to 319 in 41b9d8c

	func transceiver(c Conn, wb []byte, ch chan<- error) {
	defer close(ch)
	c.SetDeadline(time.Now().Add(someTimeout))
	c.SetReadDeadline(time.Now().Add(someTimeout))
	c.SetWriteDeadline(time.Now().Add(someTimeout))
	n, err := c.Write(wb)
	if err != nil {
	if perr := parseWriteError(err); perr != nil {
	ch <- perr
	}
	ch <- err
	return
	}
	if n != len(wb) {
	ch <- fmt.Errorf("wrote %d; want %d", n, len(wb))
	}
	rb := make([]byte, len(wb))
	n, err = c.Read(rb)
	if err != nil {
	if perr := parseReadError(err); perr != nil {
	ch <- perr
	}
	ch <- err
	return
	}
	if n != len(wb) {
	ch <- fmt.Errorf("read %d; want %d", n, len(wb))
	}
	}