net: TestListenCloseListen failures

[gopherbot]

#!watchflakes
default <- pkg == "net" && test == "TestListenCloseListen"

Issue created automatically to collect these failures.

Example (log):

=== RUN   TestListenCloseListen
    net_test.go:315: failed on try 1/10: listen tcp 127.0.0.1:48574: bind: address already in use
--- FAIL: TestListenCloseListen (0.00s)

— watchflakes

[gopherbot]

Found new dashboard test flakes for:

#!watchflakes
default <- pkg == "net" && test == "TestListenCloseListen"

2024-01-08 18:26 gotip-solaris-amd64 go@75984918 net.TestListenCloseListen (log)

=== RUN   TestListenCloseListen
    net_test.go:315: failed on try 1/10: listen tcp 127.0.0.1:48574: bind: address already in use
--- FAIL: TestListenCloseListen (0.00s)

— watchflakes

[bcmills]

This test is inherently racy:
https://cs.opensource.google/go/go/+/master:src/net/net_test.go;l=301-302;drc=a81507868344dccebef13c6d8d890633e59a93e3

Depending on the other tests running on the machine, it may have already reused the port for some other listener, perhaps even in some other test process.

Perhaps we could keep the port from being reused by leaving an open connection on it, but I wonder if that would also prevent the Listen on that port from reopening it. 🤔

(CC @ianlancetaylor @neild)

[gopherbot]

Change https://go.dev/cl/557177 mentions this issue: net: attempt to deflake TestListenCloseListen