Is this is 3-way switch, then voltage on both is normal, other wise read below.

From what it sounds like you have a SPST(single pole single throw) switch and this type of switch does not have a neutral physically attatched to it, they are typically wire-nutted together in the same box. If you are showing voltage on both wires that may be normal, because if the switch is in the on position you will measure voltage on both end the supply(from the electrical panel), and the switch leg(wire from fixture to switch). My suggestion is this, determine which wire is coming from the electrical panel, and with the power off remove the other wire from the switch, then turn the power back on and measure for voltage with the switch on and off, if you have voltage with the switch off and on then the switch is bad, but if you only have voltage when the switch is on the switch is good and your next point to measure voltage will be a the fixture, let me know what you find out.