从输入框引导程序中删除边框

I am creating a website using bootstrap, less and angular and I've been struggling all day with the input field for search bar. I tried using the bootstrap input-group with both input-group-addon and input-group-button but I cannot seem to be able to remove the border between the button and the input. Actually I cannot change the border at all. Any suggestions on how I could do this. I would like my search box have the same behaviour as in I am creating a website using bootstrap, less a