[go-server] Update dependencies and use generics

[lwj5]

The required Go version in go.mod is 1.13. Since Chi requires 1.14, this is not suitable.
Since Go versions <1.18 has been long end-of-life, and >=1.18 is required for generics 1.18 is used.

Other updates include

• bump Chi and Mux dependencies
• Change recurse to use generics

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  For Windows users, please run the script in Git BASH.
• In case you are adding a new generator, run the following additional script :

  ./bin/utils/ensure-up-to-date.sh
  

  Commit all changed files.
• File the PR against the correct branch: master (6.3.0) (minor release - breaking changes with fallbacks), 7.0.x (breaking changes without fallbacks)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

[lwj5]

@antihax (2017/11) @grokify (2018/07) @kemokemo (2018/09) @jirikuncar (2021/01) @ph4r5h4d (2021/04)

There's some issue with the CI that doesn't work with the changes. @wing328 would you be able to take a look

[wing328]

Thanks for the PR.

I'll fix the build error after merging https://github.com/OpenAPITools/openapi-generator/actions/runs/4573350282/jobs/8257105941?pr=15087