grpc-node TLS sample code is not complete.

Hi gurus,
I am a newbee to node.js and grpc. So a good sample code is really appreciated.

The grpc-node TLS sample code is in https://grpc.io/docs/guides/auth.html#nodejs not complete.
For example, no sample code for TLS client side.
The strange thing is,
https://grpc.io/grpc/node/grpc.credentials.html
createSsl( [root_certs] [, private_key] [, cert_chain])
Create an SSL Credentials object. If using a client-side certificate, both the second and third arguments must be passed.
Why are private key and cert chain needed for client side?
They are not needed for grpc-go TLS client side.
https://github.com/grpc/grpc-go/issues/1980