GoLang Tutorial - AWS SDK for Go (S3 listing)

aws-sdk-go is the official AWS SDK for the Go programming language.

The SDK is composed of two main components, SDK core, and service clients.

The SDK core packages are all available under the aws package at the root of the SDK. Each client for a supported AWS service is available within its own package under the service folder at the root of the SDK.

1. aws - SDK core: it provides common shared types such as Config, Logger, and utilities to make working with API parameters easier.
2. service - Clients: is is for AWS services. All services supported by the SDK are available under this folder.

Use go get to retrieve the SDK to add it to our GOPATH workspace, or project's Go module dependencies:

$ go get github.com/aws/aws-sdk-go
go: finding github.com/aws/aws-sdk-go v1.19.23
go: finding github.com/jmespath/go-jmespath v0.0.0-20180206201540-c2b33e8439af
go: downloading github.com/aws/aws-sdk-go v1.19.23
go: extracting github.com/aws/aws-sdk-go v1.19.23

This will add the following line to go.mod:

require github.com/aws/aws-sdk-go v1.19.23 // indirect

For more on module, please visit Modules 1 (Creating a new module) or Modules 2 (Adding Dependencies).

To update the SDK use go get -u to retrieve the latest version of the SDK:

$ go get -u github.com/aws/aws-sdk-go
go: finding github.com/jmespath/go-jmespath latest

Because we're using Go modules, our go get defaulted to the latest tagged release version of the SDK. To get a specific release version of the SDK use @<tag> in our go get command:

$ go get github.com/aws/aws-sdk-go@v1.15.77

To get the latest SDK repository change use @latest.

$ go get github.com/aws/aws-sdk-go@latest

The following sample from wsdocs/aws-doc-sdk-examples lists the buckets in our account. There are no command line arguments.

The code: s3_list_buckets.go

First, it adds the following statements to import the Go and AWS SDK for Go packages used in the example:

import (
    "github.com/aws/aws-sdk-go/aws"
    "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/s3"
    "fmt"
    "os"
)

Then, creates a function we use to display errors and exit:

func exitErrorf(msg string, args ...interface{}) {
    fmt.Fprintf(os.Stderr, msg+"\n", args...)
    os.Exit(1)
}

Note that a parameter type prefixed with three dots (...) is used. It is called a variadic parameter. That means we can pass any number or arguments into that parameter (check Passing arguments to ... parameters).

Initialize the session that the SDK uses to load credentials from the shared credentials file ~/.aws/credentials, and create a new Amazon S3 service client:

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

// Create S3 service client
svc := s3.New(sess)

Next, calls ListBuckets. Passing nil means no filters are applied to the returned list. If an error occurs, call exitErrorf. If no error occurs, loop through the buckets, printing the name and creation date of each bucket.

result, err := svc.ListBuckets(nil)
if err != nil {
    exitErrorf("Unable to list buckets, %v", err)
}

fmt.Println("Buckets:")

for _, b := range result.Buckets {
    fmt.Printf("* %s created on %s\n",
        aws.StringValue(b.Name), aws.TimeValue(b.CreationDate))
}

Go Tutorial

1. GoLang Tutorial - HelloWorld
2. Calling code in an external package & go.mod / go.sum files
3. Workspaces
4. Workspaces II
5. Visual Studio Code
6. Data Types and Variables
7. byte and rune
8. Packages
9. Functions
10. Arrays and Slices
11. A function taking and returning a slice
12. Conditionals
13. Loops
14. Maps
15. Range
16. Pointers
17. Closures and Anonymous Functions
18. Structs and receiver methods
19. Value or Pointer Receivers
20. Interfaces
21. Web Application Part 0 (Introduction)
22. Web Application Part 1 (Basic)
23. Web Application Part 2 (Using net/http)
24. Web Application Part 3 (Adding "edit" capability)
25. Web Application Part 4 (Handling non-existent pages and saving pages)
26. Web Application Part 5 (Error handling and template caching)
27. Web Application Part 6 (Validating the title with a regular expression)
28. Web Application Part 7 (Function Literals and Closures)
29. Building Docker image and deploying Go application to a Kubernetes cluster (minikube)
30. Serverless Framework (Serverless Application Model-SAM)
31. Serverless Web API with AWS Lambda
32. Arrays vs Slices with an array left rotation sample
33. Variadic Functions
34. Goroutines
35. Channels ("<-")
36. Channels ("<-") with Select
37. Channels ("<-") with worker pools
38. Defer
39. GoLang Panic and Recover
40. String Formatting
41. JSON
42. SQLite
43. Modules 0: Using External Go Modules from GitHub
44. Modules 1 (Creating a new module)
45. Modules 2 (Adding Dependencies)
46. AWS SDK for Go (S3 listing)
47. Linked List
48. Binary Search Tree (BST) Part 1 (Tree/Node structs with insert and print functions)
49. Go Application Authentication I (BasicAuth, Bearer-Token-Based Authentication)
50. Go Application Authentication II (JWT Authentication)