Add Redirect code

As Go Web server is not using Apache and therefore not using the “. htaccess” file, you must do your own redirects in Go. I can think of three redirects.

1. Static files like sitemap.xml and robots.txt.
2. Redirect historically deleted pages.
3. Show a 404 page if the page does not exist at all.

In a separate Go file I put all the redirects, as it can grow to be rather big if you have cleaned your site and got many old paths.

func redirect(w http.ResponseWriter, r *http.Request) {
  path := strings.Trim(r.URL.Path, "/")
  switch path {
  case "topnav", "sidenav":
    http.Redirect(w, r, "/navigation", http.StatusMovedPermanently)
  case "staticfiles":
    http.Redirect(w, r, "/robots", http.StatusMovedPermanently)
  case "go":
    http.Redirect(w, r, "/golang", http.StatusMovedPermanently)
  //notfound
  default:
    w.WriteHeader(http.StatusNotFound)
    tpl.ExecuteTemplate(w, "notfound.html", "")
    log("404: " + path)
  }
}