conn: lazily allocate stream call
conn: lazily allocate stream call

Use sync.Pool to recycle inflight call requests.
Use a map to store inflight requests

Zariel/gocql,vrischmann/gocql,nikandfor/gocql,znly/gocql,gocql/gocql,gus/gocql,Zariel/gocql,gocql/gocql,CrowdSurge/gocql,gus/gocql,aai/gocql,i/gocql,revinate/gocql,revinate/gocql,mailgun/gocql,CrowdSurge/gocql,znly/gocql,vrischmann/gocql,nikandfor/gocql,aai/gocql,i/gocql,ChannelMeter/gocql,nikandfor/gocql,mailgun/gocql,ChannelMeter/gocql