fix: making the examples thread-safe

[xBlaz3kx]

Proposed changes

Current example implementation may result in race conditions when under load.

• Added server client map mutexes
• Improved shutdown of example servers

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)

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Further comments

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