dial:x509: certificate signed by unknown authority in EC2 instance

Question

I have created a client that connects to an external service through websocket. The protocol is wss and the port is not constant. The application works well when tested locally on window, but when uploaded to aws ec2, the following error occurs.

dial:x509: certificate signed by unknown authority

It was written in Golang, and the ec2 image is AMI2. There are also files ca-bundle.crt and ca-bundle.trust.crt under the /etc/ssl/certs/ path. I don't want to assign a domain to this client server. (I wonder if I need to do something like creating Server.crt) I wonder what the cause is and how to fix it.