in src/GCPUnaryCall.php [43:49]
public function start($argument, $metadata, $options)
{
$channel_ref = $this->_rpcPreProcess($argument);
$real_channel = $channel_ref->getRealChannel($this->gcp_channel->credentials);
$this->createRealCall($real_channel);
$this->real_call->start($argument, $metadata, $options);
}