Hello, everyone! I am trying to perform the numerical integration of the function \tanh^2(z) using QuadGK.jl with the following code

```
using Plots
using QuadGK
k(z) = tanh(z)^2
plot(k)
Q = quadgk(k,-Inf,Inf)
```

but when I try to run, I receive the following error message

```
DomainError with -0.9999999999999964:
integrand produced Inf in the interval (-1.0, -0.9999999999999929)
```

I’m not understanding why, since \tanh^2z does not diverge for any z. Does anyone know whats happening?