ConnPool.Get blocked by slow connections

[yogipatel]

I'm connecting to a server that is taking ~10 seconds to connect to. Using the connection pool, I'm observing an odd behavior where even if there are free connections available, ConnPool.Get is blocking until the other connection completes. Once established, everything seems to work as expected, but cold starts are painfully slow, particularly when a large pool is used (I believe the default is 100 connections).

On a cursory look, the pooling implementation's use of both poolGuard and poolMutex looks a bit suspect, but I haven't thought about it too much. If this isn't by design, perhaps we can figure out a way to handle this case?