Passing arguments with action client

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I want to control an Franka Emika robot using action servers. https://frankaemika.github.io/docs/ro... The gripper Operation franka_gripper::HomingAction() is working with:

 actionlib::SimpleActionClient<franka_gripper::HomingAction> ac("franka_gripper/homing", true);
 ROS_INFO("Waiting for action server to start.");
 bool success=ac.isServerConnected(); //will wait for infinite time
 if (success)
   {ROS_INFO("Verbindung hergestellt");}
 ac.waitForServer(); 
 ROS_INFO("Action server started, sending goal.");
 franka_gripper::HomingGoal goal;
 ac.sendGoal(goal);

Now I would like to use the MoveAction as descriped in the documentation where I have to pass the arguments for width and speed. However I don't get how to do this. I checked the MoveGoal.msg which tells that two floats are needed. I tried to set them with:

ac.sendGoal(width, speed);

which is not working. Analogously to the tutorial ( http://wiki.ros.org/actionlib_tutoria... ) I used goal.order= in different variation like

goal.order {width, speed};

but it seems not to know the order function. So my question is how I can set this parameters correctly.