code: func AssertCertificateHasServerAuthUsage(t *testing.T, cert *x509.Certificate) {
  	for i := range cert.ExtKeyUsage {
  		if cert.ExtKeyUsage[i] == x509.ExtKeyUsageServerAuth {
  			return
  		}
  	}
  	t.Error("cert is not a ServerAuth")
  }
docs: // AssertCertificateHasServerAuthUsage is a utility function for kubeadm testing that asserts if a given certificate has
  // the expected ExtKeyUsageServerAuth