Function execute_cql_reader 

pub async fn execute_cql_reader<R: BufRead>(
    session: &mut CqlSession,
    config: &MergedConfig,
    colorizer: &CqlColorizer,
    reader: R,
    source_name: &str,
    writer: &mut dyn Write,
) -> i32

Execute CQL statements from any BufRead source (file or stdin).

Returns exit code: 0 on success, 1 on any CQL or I/O error.