[go] Use types to encode and decode jsonrpc queries (#372)

* use types to encode and decode jsonrpc queries

* Apply suggestions from code review

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* reexport some types

* fix race

* fix test

* export PingResponse

* use SendAndWait instead of GetFinalAssistantMessage

* fix nil access

* fix nil access

* fix nil access

* fix nil access

* fix race

* remove if

* remove getFinalAssistantMessage from nodejs test harness

* revert test changes

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: qmuntal