Function default_credentials 

pub async fn default_credentials(
    env: &AwsEnv,
    profile: Option<&str>,
    region: Option<&str>,
    cancel: &CancellationToken,
) -> Result<Credentials, String>

The default credential chain for profile (else AWS_PROFILE), with region for Security Token Service (STS) calls. Results are cached until five minutes before they expire.