code: func removeCookie(rw http.ResponseWriter, r *http.Request, cookie string) {
  	if prev, err := r.Cookie(cookie); err == nil {
  		cpy := *prev
  		cpy.Value = "deleted"
  		cpy.Path = "/"
  		cpy.MaxAge = -1
  		cpy.Expires = time.Unix(1, 0)
  		http.SetCookie(rw, &cpy)
  	}
  }
docs: // removeCookie sets a cookie to past expiration date so that browser can remove
  // it. Also replaced value with junk, in case browser decides to ignore
  // expiration time.