code: func setBrokerOption(k, v interface{}) broker.Option {
  	return func(o *broker.Options) {
  		if o.Context == nil {
  			o.Context = context.Background()
  		}
  		o.Context = context.WithValue(o.Context, k, v)
  	}
  }
docs: // setBrokerOption returns a function to setup a context with given value