--- FAIL: TestClientCallsCloseOnlyOnce (21.04s)
client_test.go:2063: dial tcp 127.0.0.1:51357: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.
FAIL net/http 25.262s
greplogs --dashboard -md -l -e '(?m)FAIL: TestClientCallsCloseOnlyOnce.*\n.*host has failed to respond'
This test creates 50 HTTP client connections, in sequence, to the same server. The error seems to indicate that one of them failed. I don't know what might cause this, but the fact that the failure has happened once in a year and only on Windows makes this hard to diagnose; I suspect it's an issue on the builder, but I don't know what. Something applying a rate limit to connection attempts?
Given the rarity of the failure, this is probably not a priority.
I wonder if the fact that it happens on both arm 32 and 64 bit is significant? I agree that it seems really hard to diagnose when it happens this rarely. I can attempt to get it to happen with brute force running on my parallels VM, but I can not leave any guarantees of success.