code: func (api UsersAPI) GetAvatarImage(w http.ResponseWriter, r *http.Request) {
  	hash := mux.Vars(r)["hash"]
  	userMgr := user.NewManager(r)
  	file, err := userMgr.GetAvatarFile(hash)
  	if handleServerError(w, "getting avatar file", err) {
  		return
  	}
  	if file == nil {
  		http.Error(w, http.StatusText(http.StatusNotFound), http.StatusNotFound)
  		return
  	}
  	w.WriteHeader(http.StatusOK)
  	w.Write(file)
  }
docs: // GetAvatarImage is the handler for GET /users/avatar/img/{hash}
  // Get the avatar file associated with this id