My node.js https client always works regardless of certificate validity

This test program connects to an https server and gets some content. I’ve checked my server in browsers and with curl and the certificate is working correctly. If I run curl to grab data from the server it correctly complains about the certificate being unknown unless I pass it in with –cacert or turn security off with -k.

Httpclient This instance has already started one or more requests. Properties can only be modified before sending the first request

I am creating an application in .Net Core 2.1 and I am using http client for web requests. The issue is I have to send parallel calls to save time and for that I am using Task.WhenAll() method but when I hit this method I get the error “This instance has already started one or more requests. Properties can only be modified before sending the first request” Previously I was using RestSharp and everything was fine but I want to use httpclient. Here is the code:

Posting to a Web API using HttpClient and Web API method [FromBody] parameter ends up being null

I am attempting to POST to a Web API using the HttpClient. When I put a breakpoint in the Save method of the Web API the [FromBody] Product is null. This means that something is wrong with the way I am posting the product over to the Web API. Can someone please take a look at the below code and see where I might be going wrong. I am assuming it is something to do with headers and content types.