Hi estegemoller,
This thread has some different examples that hopefully will get you started (just ignore the C# part):
https://forum.rclone.org/t/c-code-for-rclone-copy/33990/2
https://forum.rclone.org/t/c-code-for-rclone-copy/33990/11
https://forum.rclone.org/t/c-code-for-rclone-copy/33990/13
Here is a search to find some of my other examples:
https://forum.rclone.org/search?expanded=true&q=%22POST%20http%3A%2F%2Flocalhost%3A5572%22%20%40Ole
Just ask if the above examples are unclear or you need something else.
Happy POSTing 