Changes:

```
* backend/s3: Support for AWS Single-Sign On (SSO) cached credentials
```

Updated via:

```
go get github.com/aws/aws-sdk-go@v1.37.0
go mod tidy
```

Please note that Terraform CLI will not initiate or perform the AWS SSO login flow. It is expected that you have already performed the SSO login flow using AWS CLI using the `aws sso login` command, or by some other mechanism before executing Terraform. More precisely, this credential handling must find a valid non-expired access token for the AWS SSO user portal URL in `~/.aws/sso/cache`. If a cached token is not found, is expired, or the file is malformed an error will be returned.

You can use configure AWS SSO credentials from the AWS shared configuration file by specifying the required keys in the profile:

```
sso_account_id
sso_region
sso_role_name
sso_start_url
```

For example, the following defines a profile "devsso" and specifies the AWS SSO parameters that defines the target account, role, sign-on portal, and the region where the user portal is located. Note: all SSO arguments must be provided, or an error will be returned.

```
[profile devsso]
sso_start_url = https:my-sso-portal.awsapps.com/start
sso_role_name = SSOReadOnlyRole
sso_region = us-east-1
sso_account_id = 123456789012
```

Additional Resources

* [Configuring the AWS CLI to use AWS Single Sign-On](https:docs.aws.amazon.com/cli/latest/userguide/cli-configure-sso.html)
* [AWS Single Sign-On User Guide](https:docs.aws.amazon.com/singlesignon/latest/userguide/what-is.html)