@Deprecated
    public synchronized void setSTSClientEndpoint(String endpoint) {
        securityTokenService.setEndpoint(endpoint);
        // Create a new task rather then trying to synchronize this in the refreshable task
        this.refreshableTask = createRefreshableTask();
    }
Sets the AWS Security Token Service (STS) endpoint where session credentials are retrieved
from. <p> </p> The default AWS Security Token Service (STS) endpoint ("sts.amazonaws.com")
works for all accounts that are not for China (Beijing) region or GovCloud. You only need to
change the endpoint to "sts.cn-north-1.amazonaws.com.cn" when you are requesting session
credentials for services in China(Beijing) region or "sts.us-gov-west-1.amazonaws.com" for
GovCloud. <p> </p> Setting this invalidates existing session credentials. Calling this method
will temporarily cause getCredentials() to block until a new session is fetched from the STS
service.

@deprecated This method may be removed in a future major version. Create multiple providers
if you need to work with multiple STS endpoints.
aws-java-sdk-sts/src/main/java/com/amazonaws/auth/STSSessionCredentialsProvider.java