Bump Go to 1.18

I have bumped the version of the Go Docker image to 1.18. I have tested it and can confirm that build succeeds and it runs without issues.

Furthermore, I have removed host networking mode from docker-compose.yml, as I have found it is unnecessary, due to the fact that Snowflake doesn't actually listen on any ports. I have run an instance without host networking for 3 days non-stop now, and it works perfectly (it also runs with the Go 1.18 modification). No longer true.