made a prime number generator to do a little bit of testing

util/primes.go

@@ -0,0 +1,34 @@
+package util
+
+import (
+	"math"
+)
+
+// GeneratePrimes returns the n-th prime number
+// its param primes []int is intended to contain previously found prime numbers
+// to reduce duplicated work, but still be testable
+func GeneratePrimes(primes []int, n int) int {
+	if len(primes) < 2 {
+		primes = []int{2, 3}
+	}
+	if len(primes) >= n {
+		return primes[n-1]
+	}
+	for i := primes[len(primes)-1] + 2; len(primes) <= n; i += 2 {
+		// check if i is a prime number by checking if it is divisible by any of the previous values of primes
+		// stop at the square root of i
+		for _, v := range primes {
+			// not a prime, stop this loop
+			if i%v == 0 {
+				break
+			}
+			if math.Sqrt(float64(i)) < float64(v) {
+				// add to primes
+				primes = append(primes, i)
+				break
+			}
+		}
+	}
+
+	return primes[n-1]
+}