code: func Recover(rw http.ResponseWriter, req *http.Request) {
  	RecoverJSON(rw, req) // TODO: for now. alternate format?
  }
docs: // Recover is meant to be used at the top of handlers with "defer"
  // to catch errors from MustGet, etc:
  //
  //   func handler(rw http.ResponseWriter, req *http.Request) {
  //       defer httputil.Recover(rw, req)
  //       id := req.MustGet("id")
  //       ....
  //
  // Recover will send the proper HTTP error type and message (e.g.
  // a 400 Bad Request for MustGet)