aria2c --enable-rpc=true --rpc-listen-all=true --daemon --dir=/mnt/downloads --continue=true --max-concurrent-downloads=1 --max-connection-per-server=16 --max-tries=0 --split=16 --stream-piece-selector=geom --enable-http-pipelining=true
You can find documentation for the various options here: http://aria2.sourceforge.net/manual/en/html/aria2c.html
The mutex is only used inside of SetAlive() and isAlive(), they're the only things this need to handle locking and unlocking. You don't want anything external to that calling the methods on RWMutex.