fix: possible panic in client tests

[alexandear]

What type of PR is this? (check all applicable)

• [ ] Refactor
• [ ] Feature
• [x] Bug Fix
• [ ] Optimization
• [ ] Documentation Update
• [ ] Go Version Update
• [ ] Dependency Update

Description

This PR fixes a possible panic in tests. When err is not nil in newWebsocketServer, websocketServer is nil, and defer websocketServer.Close() will panic. The same applies to the newProxyServer function.

Added/updated tests?

• [x] Yes
• [ ] No, and this is why: please replace this line with details on why tests have not been included
• [ ] I need help with writing tests

[ghost]

The change in this PR is good.

This panic is not the only problem with an error return from the function newWebsocketServer. The function newWebsocketServer leaks a listener when returning an error. That function should websocketServer.Close() when returning an error.