Determining size of AppendRows request message

I am using the Golang Storage API library to write to BigQuery. For this I am calling AppendRows() https://pkg.go.dev/cloud.google.com/go/bigquery/storage/managedwriter#ManagedStream.AppendRows.
This function has a limitation that the request size cannot be more than 10 MB otherwise an error will be returned. One way I can avoid this is to send the data in smaller chunks. But I do not want to send too small chunks and want to send as much data as possible in a chunk.

So, I want to know if there is a way I can determine the request size before sending the data to the function? This would help me to adjust the size of the message and not keep adding the data to the request.

One options is to execute a dry run before sending the data to function.

The code snippet of the dry one using Golang is given here. The dry run will give estimate the number of bytes read by the query. Hope this helps.

For your requirement, you can consider the option mentioned by @BihagKashikar.

Other option is to, Restructure the job so that each component generates smaller requests. This can be done by Sending requests with fewer rows more often, or by checking the size of the data you are trying to send and split it into several requests if needed.
Using ‘bq load’ if you insert a single long row. Splitting into multiple requests if there are multiple rows.

For more information you can refer to this document.