Fix defer with router tests

[BoD]

Sometimes, but not always, localhost can't be resolved by node - I don't know why.
This only happens with a recent version of node (recently changed by this change), and I could only reproduce with the defer with router tests, but not with the other tests which also use localhost from MockServer.url() - but I changed it there too just in case, and to please the nodejs gods.

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[martinbonnin]

This is peculiar 🤔 . Does not give any extra reason why localhost does not work? DNS, route, timeout, anything else?

If needed we can re-introduce the old nodejs version.

[BoD]

Yeah it is very odd. I see this in node's logs:

NET 99031: connect: find host localhost
NET 99031: connect: dns options { family: undefined, hints: 1024 }
HTTP 99031: sockets localhost:4002: 1 1
HTTP 99031: write ret = true
HTTP 99031: outgoing message end.
(node:99031) Warning: Setting the NODE_DEBUG environment variable to 'http' can expose sensitive data (such as passwords, tokens and authentication headers) in the resulting log.
(Use `node --trace-warnings ...` to show where the warning was created)
NET 99031: _read
NET 99031: _read wait for connection
NET 99031: afterConnect
NET 99031: destroy
NET 99031: close
NET 99031: close handle
HTTP 99031: SOCKET ERROR: connect ECONNREFUSED ::1:4002 Error: connect ECONNREFUSED ::1:4002
    at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1494:16)

Actually maybe I misinterpreted it, could it be a IPv6 issue instead?

[martinbonnin]

Actually maybe I misinterpreted it, could it be a IPv6 issue instead?

Looks like it. In that case forcing IPv4 is the good fix 👍