This is a simple gdnative plugin that uses libcurl to download files.
This is a standard cmake project. It can either be built with command line or loaded directly in visual studio. Command line example is:
mkdir build
cd build
cmake ..
make
Output bins will be placed in the project/gdnative folder. Simply copy the gdnative folder into your current godot project to use it.
An example project is located in the project folder, but the following shows basic usage: