Different results between Go's http library and Postman -- Postman works but Go doesn't

Good day. I'm trying to scrape this URL with Go:
http://us2.m2web.talk2m.com/valleycarriers/Gorman%20Bros/usr/viewon/Overview.shtm

There's a chink in the chain. I could simply send a POST request to this endopoint with the necessary parameters, just like Chrome does, but even after Chrome does that, it pops up a window on the address bar, a browser window, asking for username and password. Because Cache-Clear in response header is must-revalidate.

So I fired up Postman. And sent a POST the same url, but like this:

https`://username:password@url

And it returned three cookies. I fed these three cookies to the endpoint that serves the data I want:

https://u:p@us2.m2web.talk2m.com/valleycarriers/Gorman Bros/rcgi.bin/vows/readVars

And got results!

Postman sends two consecutive requests after sending the first request.

I tried to replace that in Go:

loginString := "account=valleycarriers&username=u&password=p&connect=connect&attempt=0"

requestLogin, err := http.NewRequest("POST", "http://u:p@us2.m2web.talk2m.com/valleycarriers/Gorman%20Bros/usr/viewon/Overview.shtm", strings.NewReader(loginString))
	if err != nil {
		log.Fatal(err)
	}

requestLogin.Header.Add("Content-Type", "application/x-www-form-urlencoded")
requestLogin.Header.Add("Content-Length", "87")
requestLogin.Header.Add("Host", "us2.m2web.talk2m.com")
requestLogin.Header.Add("Authorization", "Basic b3BlcmF0b3I6b3BlcmF0b3IxMjM=")

But this request doesn't work. It returns two cookies, but Postman retursn three. Postman returns no body, but it returns the landing page. In Postman, if I make the pass the cookies from the first request to the second requests, it returns the data I want. But in Go it just returns the landing page, again.

I tried to inspect the outgoing traffic from Go using Fiddler, but unlike Postman, Fiddler doesn't display any traffic from this endpoint.

Thanks.

If I could comment I would, but I will just say as an answer, I have found the Code->{language} option in Postman very useful. If you click on the "Code" text under "Save" in Postman desktop, it will convert every bit of your request into usually accurate code in your language of choice.

Without seeing your Postman example, full Go code, or error/status codes, it is hard for me to figure out what is wrong. This is likely the reason for downvotes on your question. If you can post these things and the autogenerated code from Postman doesn't solve your problem, I can look at the specific case and try to debug the issue, but try these steps first.