tls_server_config :
cert_file : "testdata/server.crt"
key_file : "testdata/server.key"
client_auth_type : "VerifyClientCertIfGiven"
client_ca_file : "testdata/tls-ca-chain.pem"
curve_preferences:
- CurveP256
- CurveP384
- CurveP521
- X25519