EOF error when registering about 10000 documents

OpenSearch 2.4.0
Opensearch go client

Describe the issue:
I am creating a program to index documents using go client.
After about 10000 documents have been registered, an EOF error occurs and the registration is interrupted.
I want to know the solution.

OpenSearchServer is running using the Docker Compose sample.
Docker - OpenSearch documentation.

Registration to Index executes the following process in a loop.

    req := opensearchapi.IndexRequest{
        Index:      IndexName,
        DocumentID: docId,
        Body:       document,
    insertResponse, err := req.Do(context.Background(), client)

Relevant Logs or Screenshots:

I had to close after executing the request.

I used this as a reference.