How to fetch the tags for the current EC2 instance, from Go, using only official AWS Go SDK calls.

ec2tags.go

package main

// An example of obtaining the tags for the current EC2 running instance,
// from a Go program running inside the instance, using the official AWS SDK (v1).

import (
	"errors"
	"fmt"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/ec2metadata"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/ec2"
)

// Get region and instance of current running instance, via individual metadata calls
func getRegionAndInstance() (string, string, error) {
	sess := session.New()
	svc := ec2metadata.New(sess)
	if !svc.Available() {
		return "", "", errors.New("ec2metadata service not available")
	}
	instance, err := svc.GetMetadata("instance-id")
	if err != nil {
		return "", "", fmt.Errorf("can't get instance ID: %w", err)
	}
	region, err := svc.GetMetadata("placement/region")
	if err != nil {
		return "", "", fmt.Errorf("can't get region: %w", err)
	}
	return region, instance, nil
}

// Get region and instance of current running instance, via instance identity Document
func getRegionAndInstance2() (string, string, error) {
	sess := session.New()
	svc := ec2metadata.New(sess)
	if !svc.Available() {
		return "", "", errors.New("ec2metadata service not available")
	}
	idd, err := svc.GetInstanceIdentityDocument()
	if err != nil {
		return "", "", fmt.Errorf("can't get instance identity document: %w", err)
	}
	return idd.Region, idd.InstanceID, nil
}

// Get tags for instance, given region and instance ID
func getTags(region string, instance string) (map[string]string, error) {
	sess, err := session.NewSession(&aws.Config{
		Region: aws.String(region),
	},
	)
	svc := ec2.New(sess)
	input := &ec2.DescribeTagsInput{
		Filters: []*ec2.Filter{
			{
				Name:   aws.String("resource-type"),
				Values: []*string{aws.String("instance")},
			},
			{
				Name:   aws.String("resource-id"),
				Values: []*string{aws.String(instance)},
			},
		},
	}
	tags := make(map[string]string)
	result, err := svc.DescribeTags(input)
	if err != nil {
		return tags, fmt.Errorf("ec2.DescribeTags failed: %w", err)
	}
	if result.Tags == nil {
		return tags, nil
	}
	for _, t := range result.Tags {
		if t != nil {
			k := t.Key
			v := t.Value
			if k != nil && v != nil {
				tags[*k] = *v
			}
		}
	}
	return tags, nil
}

func main() {
	{
		// Method 1: individual metadata calls
		region, instance, err := getRegionAndInstance()
		if err != nil {
			panic(err)
		}
		fmt.Printf("region = %s instance = %s (method 1)\n", region, instance)
	}
	{
		// Method 2: via instance identity document
		region, instance, err := getRegionAndInstance2()
		if err != nil {
			panic(err)
		}
		fmt.Printf("region = %s instance = %s (method 2)\n", region, instance)
		tags, err := getTags(region, instance)
		if err != nil {
			panic(err)
		}
		for k, v := range tags {
			fmt.Printf("%s = %s\n", k, v)
		}
	}
}