letsencrypt-rs-0.3.0 is not a library.
letsencrypt-rs
DEPRECATED
This crate is merged with acme-client and letsencrypt-rs is deprecated due to ISRG trademark violation.
Please see: https://github.com/onur/acme-client/issues/25 and use acme-client crate. letsencrypt-rs is a part of acme-client now.
acme-client in: