How to make use of RoundTripper as transport instead of DefaultTransport in FromURL method of HostCertificateInfo

[Ajay-1210]

We are running our code in dark site and we don't have direct access to ESX hosts, we reach to intermediate server which has access to ESX hosts. We were able to override Roundtripper for vim25client which works for all other operations except for this below case:

For adding the host to cluster we need SHA1 thumbprint of host, in-order to fetch the thumbprint we user FromURL method of HostCertificateInfo which make a tls connection to host and the transport used here is DefaultTransport.

t := vim25ClientObject.Client.DefaultTransport()
err = hostCertInfo.FromURL(&url.URL{Host: hostName}, t.TLSClientConfig)

1. Can someone please provide a solution how to make use of RoundTripper Transport in FromURL so that we could land on intermediate server from which the ESX hosts are reachable?
2. Or if there is any other solution for fetching the host thumbprint (thumbprint of x509 certificate).