code: func reportClientRPCMetrics(ctx context.Context, method string, err error, dur time.Duration) {
  	code := 0
  	if err != nil {
  		code = int(grpc.Code(err))
  	}
  	grpcClientCount.Add(ctx, 1, method, code)
  	grpcClientDuration.Add(ctx, float64(dur.Nanoseconds()/1e6), method, code)
  }
docs: // reportClientRPCMetrics sends metrics after RPC call has finished.