Investigate potential race condition on `SourceConn` struct

[0xgouda]

While working on #1316, I noticed that the RWMutex is rarely used to protect the struct fields. I have doubts that there may be some race conditions present; this is a task for me to investigate further (so I don't forget about it :) ).

[pashagolub]

By rarely you mean in #1316 or do you mean in real life?

[0xgouda]

By rarely you mean in #1316 or do you mean in real life?

I mean in general not related to a specific PR.

For example, FetchRuntimeInfo() is being called and updated in a few places concurrently, but there is no RLock() used before reading any of the RuntimeInfo struct elements anywhere.