Provider does not seem to respect proxy variables when setting up transport

[mittler-works]

In a private network with no direct or nat'ed internet access but with a forward proxy, the provider fails planning and/or applying with

HTTP Error 'Get "https://<FQDN>/api/v3/stages/user_logout/<ID>/": dial tcp <IP>:443: connect: connection timed out' without http response

while other providers work as expected when I set the http_proxy, https_proxy and no_proxy variables.

There seems to be a similar Ticket here: #271 However, the other ticket relates to terraform init. The problem with that ticket (terraform init) is not necessarily a problem with this provider, whereas this ticket relates to a plan/apply and is likely a problem with this provider.

The problem might be here - this seems to be a pretty custom transport setup and may be missing the proxy information. Maybe this stackoverflow could be helpful.

[mittler-works]

Could it be that the underlying library that this provider uses here does not support proxy configuration?

Look at the implementation here.

I think it's missing a lot of configuration described in the original http packagere here, including proxy settings.

What's the benefit of using this library instead of just using the plain http Transport? You are already including net/http in the provider class and the plain TLS Config also supports InsecureSkipVerify, if you wish for it.