You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: instance.go
    path of file: ./repos/trivy/pkg/iac/providers/aws/ec2
    
    the code of the file until where you have to start completion: package ec2

import (
	"github.com/owenrumney/squealer/pkg/squealer"

	iacTypes "github.com/aquasecurity/trivy/pkg/iac/types"
)

type Instance struct {
	Metadata        iacTypes.Metadata
	MetadataOptions MetadataOptions
	UserData        iacTypes.StringValue
	SecurityGroups  []SecurityGroup
	RootBlockDevice *BlockDevice
	EBSBlockDevices []*BlockDe
    
func NewInstance(metadata iacTypes.Metadata) *Instance {
	return &Instance{
		Metadata: metadata,
		MetadataOptions: MetadataOptions{
			Metadata:     metadata,
			HttpTokens:   iacTypes.StringDefault("optional", metadata),
			HttpEndpoint: iacTypes.StringDefault("enabled", metadata),
		},
		UserData:        iacTypes.StringDefault("", metadata),
		SecurityGroups:  []SecurityGroup{},
		RootBlockDevice: nil,
		EBSBlockDevices: nil,
	}
}