Function csr 

pub fn csr(
    rd: &mut dyn BufRead,
) -> Result<Option<CertificateSigningRequestDer<'static>>, Error>

Available on (crate features rustls or boring or acme) and crate feature rustls and crate feature std only.

Return the first certificate signing request (CSR) found in rd.

Yields the first PEM section describing a certificate signing request, or an error if a problem occurs while trying to read PEM sections.