Integral representation of the Zeta function

```lean
import Mathlib

example {s : ℂ} (h : 1 < s.re) :
    riemannZeta s = (1 / Complex.Gamma s) *
      ∫ x in Set.Ioi (0 : ℝ), (x : ℂ) ^ (s - 1) / (Real.exp x - 1) := by
  sorry
```