With GraphQL Client, how to set Expect100Continue = true

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Hi All,

My GraphQL client need to attach client certificate to call API. In the past with WebRequest, I need to set ServicePointManager.Expect100Continue = true.
Now I am re using similar code for GraphQL Client. How can I set this value? Currently I am getting error "WebException: The request was aborted. Could not create SSL/TLS secure channel."

Any help greatly appreciated!