code: func (i *Interceptor) HandleConn(ctx context.Context, stat stats.ConnStats) {
  	lab, _ := ctx.Value(tagConnKey).(prometheus.Labels)
  
  	switch in := stat.(type) {
  	case *stats.ConnBegin:
  		if in.IsClient() {
  			i.monitoring.client.connections.With(lab).Inc()
  		} else {
  			i.monitoring.server.connections.With(withUserAgentLabel(ctx, lab)).Inc()
  		}
  	case *stats.ConnEnd:
  		if in.IsClient() {
  			i.monitoring.client.connections.With(lab).Dec()
  		} else {
  			i.monitoring.server.connections.With(withUserAgentLabel(ctx, lab)).Dec()
  		}
  	}
  }
docs: // HandleConn implements stats Handler interface.