code: func (me contextValue) SetMiddleware(val interface{}) func(http.Handler) http.Handler {
  	return func(h http.Handler) http.Handler {
  		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
  			r = me.SetRequestOnce(r, val)
  			h.ServeHTTP(w, r)
  		})
  	}
  }
docs: // Returns a middleware that sets the value in the Request's Context.