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AWS SDK for Go
Developer Guide

Configuring the AWS SDK for Go

In the AWS SDK for Go, you can configure settings for service clients, such as the log level and maximum number of retries. Most settings are optional. However, for each service client, you must specify a region and your credentials. The SDK uses these values to send requests to the correct AWS Region and sign requests with the correct credentials. You can specify these values as part of a session or as environment variables.

Specifying the AWS Region

When you specify the region, you specify where to send requests, such as us-west-2 or us-east-2. The SDK does not select a default region. For a list of regions for each service, see Regions and Endpoints in the Amazon Web Services General Reference.

To specify the region, set the AWS_REGION environment variable or specify it in a session. If you do both, the SDK will always use the region you specified in the session.

The following examples show you how to configure the environment variable.

Linux, OS X, or Unix

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$ export AWS_REGION=us-west-2

Windows

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> set AWS_REGION=us-west-2

The following snippet specifies the region in a session:

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

Specifying Credentials

The AWS SDK for Go requires credentials (an access key and secret access key) to sign requests to AWS. You can specify your credentials in several different locations, depending on your particular use case. For information about obtaining credentials, see Setting Up.

When you initialize a new service client without providing any credential arguments, the SDK uses the default credential provider chain to find AWS credentials. The SDK uses the first provider in the chain that returns credentials without an error. The default provider chain looks for credentials in the following order:

  1. Environment variables.

  2. Shared credentials file.

  3. If your application is running on an Amazon EC2 instance, IAM role for Amazon EC2.

The SDK detects and uses the built-in providers automatically, without requiring manual configurations. For example, if you use IAM roles for Amazon EC2 instances, your applications automatically use the instance's credentials. You don't need to manually configure credentials in your application.

As a best practice, AWS recommends that you specify credentials in the following order:

  1. Use IAM roles for Amazon EC2 (if your application is running on an Amazon EC2 instance).

    IAM roles provide applications on the instance temporary security credentials to make AWS calls. IAM roles provide an easy way to distribute and manage credentials on multiple Amazon EC2 instances.

  2. Use a shared credentials file.

    This credentials file is the same one used by other SDKs and the AWS CLI. If you're already using a shared credentials file, you can also use it for this purpose.

  3. Use environment variables.

    Setting environment variables is useful if you're doing development work on a machine other than an Amazon EC2 instance.

  4. Hard-code credentials (not recommended).

    Hard-coding credentials in your application can make it difficult to manage and rotate those credentials. Use this method only for small personal scripts or testing purposes. Do not submit code with credentials to source control.

IAM Roles for Amazon EC2 Instances

If you are running your application on an Amazon EC2 instance, you can use the instance's IAM role to get temporary security credentials to make calls to AWS.

If you have configured your instance to use IAM roles, the SDK uses these credentials for your application automatically. You don't need to manually specify these credentials.

Shared Credentials File

A credential file is a plaintext file that contains your access keys. The file must be on the same machine on which you're running your application. The file must be named credentials and located in the .aws/ folder in your home directory. The home directory can vary by operating system. In Windows, you can refer to your home directory by using the environment variable %UserProfile%. In Unix-like systems, you can use the environment variable $HOME or ~ (tilde).

If you already use this file for other SDKs and tools (like the AWS CLI), you don't need to change anything to use the files in this SDK. If you use different credentials for different tools or applications, you can use profiles to configure multiple access keys in the same configuration file.

Creating the Credentials File

If you don't have a shared credentials file (.aws/credentials), you can use any text editor to create one in your home directory. Add the following content to your credentials file, replacing <YOUR_ACCESS_KEY_ID> and <YOUR_SECRET_ACCESS_KEY> with your credentials.

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[default] aws_access_key_id = <YOUR_ACCESS_KEY_ID> aws_secret_access_key = <YOUR_SECRET_ACCESS_KEY>

The [default] heading defines credentials for the default profile, which the SDK will use unless you configure it to use another profile.

You can also use temporary security credentials by adding the session tokens to your profile, as shown in the following example:

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[temp] aws_access_key_id = <YOUR_TEMP_ACCESS_KEY_ID> aws_secret_access_key = <YOUR_TEMP_SECRET_ACCESS_KEY> aws_session_token = <YOUR_SESSION_TOKEN>

Specifying Profiles

You can include multiple access keys in the same configuration file by associating each set of access keys with a profile. For example, in your credentials file, you can declare multiple profiles, as follows.

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[default] aws_access_key_id = <YOUR_DEFAULT_ACCESS_KEY_ID> aws_secret_access_key = <YOUR_DEFAULT_SECRET_ACCESS_KEY> [test-account] aws_access_key_id = <YOUR_TEST_ACCESS_KEY_ID> aws_secret_access_key = <YOUR_TEST_SECRET_ACCESS_KEY> [prod-account] ; work profile aws_access_key_id = <YOUR_PROD_ACCESS_KEY_ID> aws_secret_access_key = <YOUR_PROD_SECRET_ACCESS_KEY>

By default, the SDK checks the AWS_PROFILE environment variable to determine which profile to use. If no AWS_PROFILE variable is set, the SDK uses the default profile.

If you have an application named myapp that uses the SDK, you can run it with the test credentials by setting the variable to test-account myapp, as shown in the following command.

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$ AWS_PROFILE=test-account myapp

You can also use the SDK to select a profile by specifying os.Setenv("AWS_PROFILE", test-account) before constructing any service clients or by manually setting the credential provider, as shown in the following example.

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

In addition, checking if your credentials have been found is fairly easy.

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_, err := sess.Config.Credentials.Get()

If ChainProvider is being used, set CredentialsChainVerboseErrors to true in the session config.

Note

If you specify credentials in environment variables, the SDK will always use those credentials, no matter which profile you specify.

Environment Variables

By default, the SDK detects AWS credentials set in your environment and uses them to sign requests to AWS. That way you don't need to manage credentials in your applications.

The SDK looks for credentials in the following environment variables:

  • AWS_ACCESS_KEY_ID

  • AWS_SECRET_ACCESS_KEY

  • AWS_SESSION_TOKEN (optional)

The following examples show how you configure the environment variables.

Linux, OS X, or Unix

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$ export AWS_ACCESS_KEY_ID=YOUR_AKID $ export AWS_SECRET_ACCESS_KEY=YOUR_SECRET_KEY $ export AWS_SESSION_TOKEN=TOKEN

Windows

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> set AWS_ACCESS_KEY_ID=YOUR_AKID > set AWS_SECRET_ACCESS_KEY=YOUR_SECRET_KEY > set AWS_SESSION_TOKEN=TOKEN

Warning

Do not embed credentials inside an application. Use this method only for testing purposes.

You can hard-code credentials in your application by passing the access keys to a configuration instance, as shown in the following snippet.

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sess, err := session.NewSession(&aws.Config{ Region: aws.String("us-west-2"), Credentials: credentials.NewStaticCredentials("AKID", "SECRET_KEY", "TOKEN"), })

Other Credentials Providers

The SDK provides other methods for retrieving credentials in the aws/credentials package. For example, you can retrieve temporary security credentials from AWS Security Token Service or credentials from encrypted storage. For more information, see Credentials.

Configuring a Proxy

If you cannot directly connect to the internet, you can use Go-supported environment variables (HTTP_PROXY) or create a custom HTTP client to configure your proxy. Use the Config.HTTPClient struct to specify a custom HTTP client. For more information about how to create an HTTP client to use a proxy, see the Transport struct in the Go http package.