fix(plc4go/codegen): Truly close connection

[hongjinlin]

When closing the connection and reconnecting, it keeps reporting "Connection refused" error, and after checking, I found that the Close function does not really close the connection.

[chrisdutz]

Hi hongjinlin ... just one question ... as at Apache most communication is done via mailinglists ... could you please subscribe to the dev@plc4x.apache.org mailinglis (by sending an empty email to dev-subscribe@plc4x.apache.org) and tell us a bit on what you are working on?

We're really happy about your PRs and would like to get to know you a bit better :-)

[hongjinlin]

Hi hongjinlin ... just one question ... as at Apache most communication is done via mailinglists ... could you please subscribe to the dev@plc4x.apache.org mailinglis (by sending an empty email to dev-subscribe@plc4x.apache.org) and tell us a bit on what you are working on?

We're really happy about your PRs and would like to get to know you a bit better :-)

I'll post when I have time, thank you very much!