private String getTokenValue() {
            if (System.getenv(CONTAINER_AUTHORIZATION_TOKEN) != null) {
                return System.getenv(CONTAINER_AUTHORIZATION_TOKEN);
            } else if (System.getenv(CONTAINER_AUTHORIZATION_TOKEN_FILE) != null) {
                String tokenFile = System.getenv(CONTAINER_AUTHORIZATION_TOKEN_FILE);
                return readToken(tokenFile);
            }
            return null;
        }
A URI resolver that uses environment variable {@value CONTAINER_CREDENTIALS_FULL_URI} as the URI
for the metadata service.
Optionally an authorization token can be provided using the {@value CONTAINER_AUTHORIZATION_TOKEN} environment variable.
aws-java-sdk-core/src/main/java/com/amazonaws/auth/ContainerCredentialsProvider.java