* feat: unary Ping method for geyser_server
* fix: variables can be used directly in the `format!` string
* feat: Geyser server getLatestBlockhash method
* fix: use RwLock from tokio
by fanatid:
I think it's better to use RwLock from tokio, everything what we have is async
* feat: #112 getBlockHeight & getSlot
* use RwLock and mpsc (#118)
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Co-authored-by: Kirill Fomichev <fanatid@ya.ru>