How to make a pointer member data's constness vary with the parent instance's constness?

I have a class like this one:

struct Example
{
    std::unique_ptr<int> pointer_member;
};

I'd like the type of pointer_member to be std::unique_ptr<int const> const when manipulating instances of Example const, and std::unique_ptr<int> when manipulating instances of Example.

The best solution I could think of so far involves templates, but it's really boilerplaty and not very usable (because the template arguments propagate to the code working with Example):

template <bool is_const>
struct Example
{
    std::unique_ptr<std::conditional_t<is_const, int const, int>> pointer_member;
};

Also here, nothing prevents me from using Example<false> const instances and it's really annoying.

Any idea of how to achieve this in a better way?

Solution

Encapsulation allows to control modifiable-ness (aka constness) of members:

#include <memory>
struct Example {
    const int& get() const {
        return *pointer_member;
    }
    int& get() {
        return *pointer_member;
    }
private:
    std::unique_ptr<int> pointer_member = std::make_unique<int>(42);
};


int main(){
    const Example ex1;
    const int& const_ref = ex1.get();
    Example ex2;
    ex2.get() = 123;
}