code: func reportServerRPCMetrics(ctx context.Context, method string, code codes.Code, dur time.Duration) {
  	grpcServerCount.Add(ctx, 1, method, int(code))
  	grpcServerDuration.Add(ctx, float64(dur.Nanoseconds()/1e6), method, int(code))
  }
docs: // reportServerRPCMetrics sends metrics after RPC handler has finished.