Use Gauss' law to find the electric field of an infinitely long wire with static, uniform charge density (lambda) at some distaance r from it. Integrate to get the potential V(r), using V(r)-V(ro)=- \(\int_{r_o{}}^{r} E dl\)
where r0 is some reference point. Often we choose the reference point to be innity and set V = 0 there. What happens if you try to do that here?