code: func (o OAuth) NewTokensFromRequest(req *http.Request) (*oauthTokens, error) {
  	query := req.URL.Query()
  	code := query.Get("code")
  	return o.GetTokens(code, "authorization_code")
  }
docs: // NewTokensRequest generates new tokens for OAuth user given an http request
  // containing the query parameter 'code'