upload file stuck when I set AWS_SECRET_ACCESS_KEY to empty

[godzilla-s]

Database name

Wal-g provides support for many databases, please write down name of database you uses.

Issue description

Describe your problem

When I set AWS_SECRET_ACCESS_KEY to empty, and execute wal-g wal-push to upload file to S3 bucket, it stuck. I debug it and print the message, it show:

cause by: Put "http://169.254.169.254/latest/api/token": context deadline exceeded (Client.Timeout exceeded while awaiting headers)

I tested it in an offline network environment（can not access website）

so should AWS_SECRET_ACCESS_KEY must be set?

Please provide steps to reproduce

// it can really help

Please add config and wal-g stdout/stderr logs for debug purpose

also you can use WALG_LOG_LEVEL=DEVEL for logs collecting

If you can, provide logs

```bash any logs here ```

[godzilla-s]

is it default to go to 169.254.169.254 server to request token if AWS_SECRET_ACCESS_KEY not set？

[godzilla-s]

       accessKeyId := getFirstSettingOf(settings, []string{AccessKeyIdSetting, AccessKeySetting})
	secretAccessKey := getFirstSettingOf(settings, []string{SecretAccessKeySetting, SecretKeySetting})
	sessionToken := settings[SessionTokenSetting]
	if accessKeyId != "" && secretAccessKey != "" {
		provider := &credentials.StaticProvider{Value: credentials.Value{
			AccessKeyID:     accessKeyId,
			SecretAccessKey: secretAccessKey,
			SessionToken:    sessionToken,
		}}
		providers := make([]credentials.Provider, 0)
		providers = append(providers, provider)
		providers = append(providers, defaults.CredProviders(config, defaults.Handlers())...)
		newCredentials := credentials.NewCredentials(&credentials.ChainProvider{
			VerboseErrors: aws.BoolValue(config.CredentialsChainVerboseErrors),
			Providers:     providers,
		})

		config = config.WithCredentials(newCredentials)
	}

what to do if accesskeyId and secretAccessKey is empty? use credentials.AnonymousCredentials ??

[usernamedt]

Hi! If AWS_SECRET_ACCESS_KEY is empty WAL-G will look for the credentials in ~/.aws/credentials or EC2 metadata, as described in docs.