fix: localhost not being resolved. Resolves #4460, #3564

[mikechau]

Add nsswitch.conf to resolve hosts in /etc/hosts. When cgo is disabled argo server is unable to resolve localhost. Go will fallback to check /etc/nsswitch.conf. We set nsswitch.conf to first check /etc/hosts and then dns.

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[alexec]

Excellent. Can you share an example of someone else doing this? Or the reason for this approach?

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[mikechau]

Hi @alexec, see: golang/go#22846 (comment) and golang/go#22846 (comment) for the reasoning.

We run Kubernetes on-premises and the argocli image w/ argo server didn't work for us. Enabling the cgo dns resolver or setting the /etc/nsswitch.conf with hosts: files dns did fix the issue however. When cgo is disabled, Go will fallback to /etc/nsswitch.conf to decide how to handle DNS lookups and since argocli uses scratch as its base image, I suspect it does not include a /etc/nsswitch.conf file.

Some additional prior art:

docker-library/docker#82
docker-library/docker#84