Is it possible to allow access to RDS via existing security group about cdk-gitlab-runner HOT 5 CLOSED

const runner = new GitlabContainerRunner(this, 'GitlabContainerRunner', {
      selfvpc: vpc,
      gitlabtoken: '',
    });

    defaultSecurityGroup.addIngressRule(
      ec2.Peer.securityGroupId(runner.defaultRunnerSG.securityGroupId),
      ec2.Port.tcp(5432),
      'Opening RDS to Lambda',
    );

const vpc = new ec2.Vpc(this, 'VPC', {
      cidr: '10.0.0.0/20',
      natGateways: 1,
      maxAzs: 2,
      enableDnsHostnames: true,
      enableDnsSupport: true,
      subnetConfiguration: [
        {
          cidrMask: 22,
          name: 'public',
          subnetType: ec2.SubnetType.PUBLIC,
        },
        {
          cidrMask: 22,
          name: 'private',
          subnetType: ec2.SubnetType.PRIVATE_WITH_EGRESS,
        },
      ],
    });

    // my sg
    const defaultSecurityGroup = ec2.SecurityGroup.fromSecurityGroupId(
      this,
      'SG',
      vpc.vpcDefaultSecurityGroup,
    );

    defaultSecurityGroup.addIngressRule(
      ec2.Peer.securityGroupId(defaultSecurityGroup.securityGroupId),
      ec2.Port.tcp(5432),
      'Opening RDS to Lambda',
    );

    const runner = new GitlabContainerRunner(this, 'GitlabContainerRunner', {
      selfvpc: vpc,
      gitlabtoken: '',
      vpcSubnet: {
        subnetType: aws_ec2.SubnetType.PRIVATE_WITH_EGRESS,
      },
    });

    defaultSecurityGroup.addIngressRule(
      ec2.Peer.securityGroupId(runner.defaultRunnerSG.securityGroupId),
      ec2.Port.tcp(5432),
      'Opening RDS to Lambda',
    );
    new rds.DatabaseCluster(
      this,
      'Cluster',
      {
        engine: rds.DatabaseClusterEngine.AURORA_POSTGRESQL,
        parameterGroup: rds.ParameterGroup.fromParameterGroupName(
          this,
          'ParameterGroup',
          'default.aurora-postgresql13',
        ),
        instanceProps: {
          vpc,
          vpcSubnets: vpc.selectSubnets({
            subnetType: ec2.SubnetType.PUBLIC,
          }),
          instanceType: ec2.InstanceType.of(
            ec2.InstanceClass.T3,
            ec2.InstanceSize.MEDIUM,
          ),
          securityGroups: [defaultSecurityGroup],
        },
        instances: 1,
        storageEncrypted: true,
        credentials: {
          username: 'pgadmin',
          password: SecretValue.unsafePlainText('123456wsxedc'),
        },
      },
    );