Golang net: TestLookupNoSuchHost failing on plan9/386 builder

Since the migration of the plan9/386 builder, the TestLookupNoSuchHost test is failing:

--- FAIL: TestLookupNoSuchHost (0.25s)
    --- FAIL: TestLookupNoSuchHost/LookupCNAME_NXDOMAIN (0.01s)
        --- FAIL: TestLookupNoSuchHost/LookupCNAME_NXDOMAIN/default_resolver (0.01s)
            lookup_test.go:1603: unexpected success
        --- FAIL: TestLookupNoSuchHost/LookupCNAME_NXDOMAIN/forced_go_resolver (0.00s)
            lookup_test.go:1603: unexpected success
        --- FAIL: TestLookupNoSuchHost/LookupCNAME_NXDOMAIN/forced_cgo_resolver (0.00s)
            lookup_test.go:1603: unexpected success
net.test 21894: warning: process exceeds 100 file descriptors
net.test 22606: warning: process exceeds 200 file descriptors
net.test 23370: warning: process exceeds 300 file descriptors
FAIL
FAIL    net 24.337s

The issue is that the queryDNS function in lookupCNAME return the resource does not exist; negrcode error string, which is not handled correctly.

Comment From: gopherbot

Change https://go.dev/cl/589715 mentions this issue: net: handle more error strings in lookupCNAME on Plan 9