[jsonrpc] High number of goroutines waiting for next message

[lanzafame]

Describe the bug
nextMessage appears to be leaking goroutines

To Reproduce
Steps to reproduce the behavior:

1. Run miner for a while
2. Run pprof trace

Expected behavior
There shouldn't be this many goroutines for nextMessage.

Screenshots

Version (run lotus --version):
master

[magik6k]

There are some fixes / changes to related code in #1221 (from #1155), so any investigating should happen on the testnet/3 branch, or after it's merged

[ridewindx]

Why jsonrpc?
jsonrpc just looks like a "deprecated" rpc mechanism convention which comes from btc/eth.
New blockchain should consider grpc, it's more mature and featured, also appropriate for public api.

[magik6k]

Looks like this got fixed