Random Number Generator with mt19937 Not Working Properly

Question

The code is giving me the same number every time I run the program. I can't figure out why.

I looked up a tutorial on how to use the seed the generator properly, and for some reason my example won't work.

#include <iostream>
#include <random>

int returnRandomNumber(int to) {
    std::random_device rd;
    std::mt19937 mt(rd());
    std::uniform_int_distribution<> dist(0, to);

    return dist(mt);
}

int main() {

    int testNum;

    for (int i = 0; i < 10; i++) {

        testNum = returnRandomNumber(100);
        std::cout << testNum << "\n";

    }

}