code: func (pool *AddressBasedPool) GetConn(addr string) (IOSession, error) {
  	conn := pool.getConnLocked(addr)
  	if err := pool.checkConnect(addr, conn); err != nil {
  		return nil, err
  	}
  
  	return conn, nil
  }
docs: // GetConn returns a IOSession that connected to the address
  // Every address has only one connection in the pool