Generate a self-signed certificate like this:

openssl genrsa -des3 -out key.pem
openssl rsa -in key.pem -out key.pem
openssl req -sha256 -new -key key.pem -out csr.csr -subj '/CN=localhost'
openssl x509 -req -days 365 -in csr.csr -signkey key.pem -out cert.pem
rm csr.csr