otelgrpc's UnaryServerInterceptor cannot send metrics with correct grpc status code

[liufuyang]

Description

In this part of the code, as it is in a defer call, the statusCode seems to be always 0 and cannot be set to the actual status returned by the handler call.

opentelemetry-go-contrib/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go

Lines 370 to 375 in 5adc271

	defer func(t time.Time) {
	elapsedTime := time.Since(t) / time.Millisecond
	attr = append(attr, semconv.RPCGRPCStatusCodeKey.Int64(int64(statusCode)))
	o := metric.WithAttributes(attr...)
	cfg.rpcServerDuration.Record(ctx, int64(elapsedTime), o)
	}(time.Now())

)

I guess instead of using defer and moving that piece of code after the handler call should make it work?