Resizable child "ImGui"

I'm having a problem with my project where I can't get my ImGui::Beginchild to be resizable like ImGui::Begin()

I found other ways to do this but it was not to my liking: https://github.com/ocornut/imgui/issues/319

EXAMPLE CODE :

ui::Begin("title"){

ui::BeginChild("child title", child_size);// resize this child_size when i click the bottom of the child and move

{    
ui:Text("example");

}       

ui::EndChild();


}

ui::End();