A thing that generates certificates. Since https://letsencrypt.org/ is
also a thing, you should probably use that instead. Still, gencert can
be useful to do PKI on things that only live on your LAN.
Examples
# Install gencert.
$ go install go.awhk.org/gencert
# Generate a self-signed certificate.
# This generates ~/out/my-ca.crt and ~/out/my-ca.key.
$ gencert ca \
-c US \
-o example.com \
-cn 'My CA' \
-d $((100 * 24))h \
-out ~/out/my-ca
# Generate a normal certificate.
# This reads ~/out/my-ca.crt and ~/out/my-ca.key, and generates
# ~/out/my-site.crt and ~/my-site.key.
$ gencert cert \
-ca ~/out/my-ca \
-c US \
-o example.com \
-cn 'My Server' \
-d $((10 * 24))h \
-dns www.example.com \
-usage server-auth \
-out ~/out/my-site