Can't seem to access image form data from endpoint

I’m using Go as my backend and uikit (CSS Framework) as my front end, I’m trying to upload a file: I have limited options unless I want to extend the source but here’s the ajax call once a image is submitted:

const data = new FormData();
files.forEach(file => data.append(, file));


<div class="js-upload uk-placeholder uk-text-center">
    <span uk-icon="icon: cloud-upload"></span>
    <span class="uk-text-middle uk-margin-small-left">Attach files by dropping them here or</span>
    <div uk-form-custom>
         <input name="this_is_the_file_i_want" type="file" accept="image/png, image/jpeg" multiple>
          <span class="uk-link">selecting one</span>

Once that’s called (no errors) I’ve tried accessing the data with ParseMultipartForm and r.FormValue` but I cannot seem to get anything.

Could someone point me in the direction how to access the files?