Rust error[E0597]: does not live long enough

I am trying to simplify this nodejs-polars code.
I have path_or_buffer: Either<String, Buffer> as a function param. When trying to match:

let file = match path_or_buffer {
   Either::A(path) => Box::new(std::fs::File::open(path).unwrap()) as Box<dyn MmapBytesReader>,
   Either::B(buffer) => Box::new(Cursor::new(buffer.as_ref())) as Box<dyn MmapBytesReader>
}

I get: error[E0597]: buffer does not live long enough Thx

My solution turned to be rather simple, Box::new turned out to be the problem.

fn mmap_reader_to_df<'a>(
    csv: impl MmapBytesReader + 'a,
    options: ReadCsvOptions,
) -> napi::Result<JsDataFrame> {...}

then to call it:

pub fn read_csv(
    path_or_buffer: Either<String, Buffer>,
    options: ReadCsvOptions,
) -> napi::Result<JsDataFrame> {
    match path_or_buffer {
        Either::A(path) => mmap_reader_to_df(std::fs::File::open(path).expect("unable to read file"), options),
        Either::B(buffer) => mmap_reader_to_df(Cursor::new(buffer.as_ref()), options),
    }
}