## Summary
Comprehensive fixes for race conditions, concurrency bugs, and a critical session handling bug across the session package and its child packages.
## Changes
### Bug Fix: waitForTCPIPForward fails on non-tcpip-forward global requests
- Changed `waitForTCPIPForward()` from a single select to a for loop that drains non-tcpip-forward requests gracefully
- Non-tcpip-forward requests now receive a false reply and the function continues waiting for the actual forward request
- The 500ms timeout resets after each request to handle slow clients with multiple early requests
- Updated and added tests to cover the new behavior: Wrong_Request_Type_Then_Timeout, Multiple_Non-Forward_Requests_Then_Success, Timeout_After_Non-Forward_Requests
### Race Condition Fixes
- Added sync.RWMutex to the forwarder struct to protect concurrent field access
- Fixed data race in forwarder setters (`SetType()`, `SetForwardedPort()`, `SetListener()`) by adding `Lock()`/`Unlock()` protection
- Fixed data race in forwarder getters (`TunnelType()`, `ForwardedPort()`, `Listener()`) by adding `RLock()`/`RUnlock()` protection
- Added sync.RWMutex to the slug struct to protect concurrent field access
- Fixed data race in `slug.Set()` by adding `Lock()`/`Unlock()` protection
- Fixed data race in `slug.String()` by adding `RLock()`/`RUnlock()` protection
### Concurrency Safety Improvements
- Changed `OpenForwardedChannel()` to use `f.ForwardedPort()` getter instead of direct field access
- Fixed `Close()` in forwarder to use `f.Listener()` getter consistently instead of accessing `f.listener` directly
- Fixed data race in `HandleTCPForward()` where the goroutine running `tcpServer.Serve(listener)` wrote to the outer err variable from the enclosing function scope
- Changed err = `tcpServer.Serve(listener)` to `if err := tcpServer.Serve(listener)` so the goroutine uses a local variable
Reviewed-on: #151
Co-authored-by: Bagas <bagas@fossy.my.id>
Co-committed-by: Bagas <bagas@fossy.my.id>
bagas
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