code: func (h *baseStatsHandler) TagConn(ctx context.Context, info *stats.ConnTagInfo) context.Context {
  	return context.WithValue(ctx, tagConnKey, prometheus.Labels{
  		labelRemoteAddr:      info.RemoteAddr.String(),
  		labelLocalAddr:       info.LocalAddr.String(),
  		labelClientUserAgent: userAgent(ctx),
  	})
  }
docs: // TagRPC implements stats Handler interface.