net: implement IsConnectionBrokenError for Plan 9

[erenberg]

No description provided.

[jkralik]

@erenberg I'm not familiar with the Plan 9 OS. Could you please explain the reason for adding the IsConnectionBrokenError function?

[erenberg]

On Tuesday, January 30, 2024 8:31:45 AM CET, Jozef Kralik wrote: @erenberg I'm not familiar with the Plan 9 OS. Could you please explain the reason for adding the IsConnectionBrokenError function?

IsConnectionBrokenError is a function that is used but not implemented for Plan 9. Returning false when checking error types is standard for Go on Plan 9: https://cs.opensource.google/go/go/+/refs/tags/go1.21.6:src/net/error_plan9.go This makes go-coap work on Plan 9 and has no effect on other platforms.

[erenberg]

The other implementations of `IsConnectionBrokenError`: https://github.com/plgd-dev/go-coap/blob/master/net/error_unix.go https://github.com/plgd-dev/go-coap/blob/master/net/error_windows.go

[jkralik]

Thx for contribution 👍