The CN must be a hostname without a protocol.
With the protocol the command even fails because of the missing escaping of the forward slashes:
openssl req -x509 -newkey rsa:2048 -keyout myservice.key -out myservice.cert -days 365 -nodes -subj '/CN=https://myservice.example.com'
Generating a 2048 bit RSA private key
..+++
...........................+++
writing new private key to 'myservice.key'
-----
end of string encountered while processing type of subject name element #1
problems making Certificate Request
Signed-off-by: Bastian Hofmann <bashofmann@gmail.com>
Bastian Hofmann
Catherine Luse