test.go

package main

import (
    "fmt"

    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/ec2metadata"
    "github.com/aws/aws-sdk-go/aws/session"
)

func main() {
    sess, err := session.NewSession(&aws.Config{
        Region: aws.String("us-west-2")},
    )

    svc := ec2metadata.New(sess)
    outpostArn, err := svc.GetMetadata("outpost-arn")

    if err != nil {
        fmt.Println(err)
    } else {
        fmt.Println(outpostArn)
    }
}