I'm planning on using the Google maps API in flutter for a kind of delivery app. I plan on showing the user the estimated time of arrival that the food will be delivered to them. I have designed it so that the "warehouse" locations will be fetched from the backend and stuff and the user can only change the delivery point.
What I wish to know is how to get the ETA of the food to their doorstep/building.
I don't want to use the directions API if possible as I don't want to have to pay for it.
If possible I'd like something that works with the polyline API for flutter.
Thanks in advance.