You could use the split template function. Just insert a custom delimiter in the content files at each point where the content should continue in the next column.
Your code would look as follows. I have not tested it but you should get at least a foundation. <split> is our custom delimiter.
{{ $cols := split .Content "<split>" }}
{{ range $cols }}
<div class="content-column">
{{ . }}
</div>
{{ end }}