it depends!
I'd say yes, but you could have any number of materials, each with pros and cons...
concrete ~ cold but wash-down-able
wood, chipboard ~ warmer, might rot, get chewed, rat holes if you feed in there,
bare earth ~ will need covering in Winter, in theory urine should soak in (til you cover it in straw!)
Are you getting kids? they will run and jump to kick the shed, if they're anything like mine! So extra lining might be useful. And goats will chew the wood - we've patched ours up numerous times....
how long til you get goats? very exciting!!