in src/index.ts [226:233]
public static getOrCreate(scope: cdk.Construct) {
const vpc = scope.node.tryGetContext('use_default_vpc') === '1' ?
ec2.Vpc.fromLookup(scope, 'Vpc', { isDefault: true }) :
scope.node.tryGetContext('use_vpc_id') ?
ec2.Vpc.fromLookup(scope, 'Vpc', { vpcId: scope.node.tryGetContext('use_vpc_id') }) :
new ec2.Vpc(scope, 'Vpc', { maxAzs: 3, natGateways: 1 });
return vpc;
}