"readDefaultFile" connection property is not working when used in C++ code using mysql-connector-c++-8.0.33

I am using mysql-connector-c++-8.0.33 and C++ code to connect to database.

Here is the code,

try {
  sql::Driver *driver;
  sql::Connection *con;
  sql::Statement *stmt;
  sql::ResultSet *res;
  sql::ConnectOptionsMap connection_properties;

  driver = get_driver_instance();
  connection_properties["hostName"] = "localhost";
  connection_properties["userName"] = "correctusername";
  connection_properties["password"] = "correctpassword";
  connection_properties["schema"] = "testDB";
  connection_properties["readDefaultFile"] = "/etc/my.cnf";

  con = driver->connect(connection_properties);
  
  delete con;
}
catch(sql::SQLException &e)
{
  cout << "# ERR: " << e.what();
  cout << " (MySQL error code: " << e.getErrorCode();
  cout << ", SQLState: " << e.getSQLState() << " )" << endl;

}

In this case, when I provide "readDefaultFile" property with the file path of my.cnf that has all the data required such as socket, username, group etc, I get the below exception:

# ERR: Unable to connect to localhost (MySQL error code: 2003, SQLState: HY000 )

Instead, when I provide the "socket" property as below, the database connects.

connection_properties["socket"] = "/path/mysql.sock";

Could you please suggest if I am missing something here while using readDefaultFile? The same my.cnf file works and database connects when I use mysql++ but is not connecting using mysql-connector. Requirement is that the application should use the "readDefaultFile" property and avoid using "socket" property.

Many Thanks