This patch release actually has some notable new features but nothing that affects existing API surface:

• New private keys are generated for every renewal (unless the new config property ReusePrivateKeys is set to true) -- previously, they were reused by default.
• New IssuerPolicy field to configure how to choose from multiple issuers. By default, the first issuer that successfully provided a certificate is used. (This is unchanged.) Now, however, the issuers can be shuffled to implement basic load balancing before trying them in succession.
• File storage locking mechanism is now more robust against short-lived locks in slow storage.
• The cert_obtained event info was fixed.

(Skip v0.18.1, as it contains a bug caught by integration tests downstream.)

What's Changed

• Generate new private keys for new certificates by @mholt in https://github.com/caddyserver/certmagic/pull/237
• Issuer policies that can randomize issuer used by @mholt in https://github.com/caddyserver/certmagic/pull/238

Full Changelog: https://github.com/caddyserver/certmagic/compare/v0.18.0...v0.18.2