Libcurl authentication issues - c++

Question

I'm trying to use libcurl in C++ to send requests to a url. When I set up the request in the command line with curl, it seems to work fine:
curl -vvv -X POST -H "Authorization: <api key here>" -H "Content-Type:application/json" "<host>" --data-binary '<json data here>'
The response starts something like this:
> POST <host> HTTP/1.1
> Host: <host>
> User-Agent: curl/7.61.1
> Accept: */*
> Authorization: <api_key>
> Content-Type:application/json
> Content-Length: 80
So i can see the authorization is being sent properly.
When I try to do a similar thing in C++, using the libcurl C library, however, I don't notice the ">" in front of the request headers:
Code:
struct curl_slist *chunk = NULL;
chunk = curl_slist_append(chunk, "Authorization: <api_key>");
chunk = curl_slist_append(chunk, "Content-Type:application/json");
curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
curl_easy_setopt(curl, CURLOPT_URL, "<host>");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, "<json>");
res = curl_easy_perform(curl);
curl_easy_cleanup(curl);
Response:
> POST <host> HTTP/1.1
Host: <host>
Accept: */*
Authentication: <api_key>
Content-Type:application/json
Content-Length: 97
So I'm not even sure if the headers are even properly being processed or received by the host.
Any ideas?
I get the following response:
{
"message": "No authorization header given",
"code": 401
}

Answer 1

Incorrect Header. Should be Authorization, not Authentication.

Answer 2

In your command line verbose output the header is named "Authorization: ". In your libcurl vebose output its "Authentication: ". Authorization != Authentication?
Verbose output:
Its only a different output format for verbose between command line and libcurl. The headers are sent. Same output format is used for example by php curl. Only first line has ">" and then all following headers has no ">". But they are all submited.
PHP curl verbose example output:
* Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 80 (#0)
> GET /XXX/api.php HTTP/1.1
Host: localhost
Accept: */*
Authorization: XXX
Content-Type: application/json
< HTTP/1.1 200 OK
< Date: Mon, 31 Dec 2018 20:12:51 GMT
< Server: Apache/2.4.34 (Win32) OpenSSL/1.1.0i PHP/7.2.10
< X-Powered-By: PHP/7.2.10
< Content-Length: 2390
< Content-Type: text/html; charset=UTF-8
<
* Connection #0 to host localhost left intact