Add a benchmark iteration arount the CreateDHSessionKey function call

diffieHellman/dhkx_test.go

@@ -261,7 +261,8 @@ func BenchmarkCreateDHSessionKey(b *testing.B) {
 	privKey, _ := CreateDHKeyPair(grp)
 
 	b.ResetTimer()
-
+	for n := 0; n < b.N; n++ {
 		CreateDHSessionKey(pubKey, privKey, grp)
 
 	}
+}