How to send http.post() in the background?

Question

Dart

Good afternoon.
Can you please tell me how to correctly specify the http.post() request so that it continues to work in the background for the carp_background_location plugin (or any other plugin, if this one does not fit). As a code, I use an example of this plugin.

If the application goes into the background, then http.post() is not passed, although the plugin continues to work.