Golang function to split a string by size on a separator.

SplitAfterNSize

func StringSplitAfterNSize(s, sep string, size int) (resp []string) {
	rl := ""
	for _, line := range strings.SplitAfter(s, sep) {
		if len(rl+line) > size {
			resp = append(resp, rl)
			rl = ""
		}
		rl += line
	}
	if len(resp) > 0 && len(rl) == 0 {
		return
	}
	resp = append(resp, rl)
	return
}