How to pass an aws IAM role to a Java client (through a lambda function) - amazon-web-services

Question

I'm aiming to create a lambda function which it will execute a java client, such (the java client) is supposed to call an aws service endpoint.
Since my java client needs authentication (I am approaching this with the AWS4Signer library). I would like to authenticate my java code with the IMDS of my lambda exception role, as I can't use users due to a sec procedures.
I've been trying to use InstanceProfileCredentialsProvider as my credential provider
https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/java-dg-roles.html
which in theory it should take the IMDS of the instance.Not sure if it only when using an EC2 instance, or it could also work with any aws compute service, such as lambda is.
with InstanceProfileCredentialsProvider I'm getting the following error:
com.amazonaws.internal.InstanceMetadataServiceResourceFetcher - Token is not supported. Ignoring
Failed to connect to service endpoint: com.amazonaws.SdkClientException: Failed to connect to service endpoint:
at com.amazonaws.internal.EC2ResourceFetcher.doReadResource(EC2ResourceFetcher.java:100)
I came across with the following blogs where a similar issue was resported
https://github.com/aws/aws-sdk-java/issues/2285
https://medium.com/expedia-group-tech/service-slow-to-retrieve-aws-credentials-ebc02a38e95b
and it seems this is happening due to the catched instance credentials is already outdated at the time to authenticate the credentials.
So I have added a logic to refresh the credentialsProvider object (InstanceProfileCredentialsProvider)
public static Optional<AWSCredentials> retrieveCredentials (AWSCredentialsProvider provider){
var attempts = 0;
System.out.println("Retrieving credentials...");
try {
System.out.printf("Retrieving credentials at attempt : %s", attempts);
return Optional.of(provider.getCredentials());
}catch(Exception e){
while(attempts < 15) {
try {
TimeUnit.SECONDS.sleep(30);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
System.out.printf("Retrieving credentials at attempt : %s", attempts);
provider.refresh();
try {
return Optional.of(provider.getCredentials());
}catch (Exception e1){
System.out.printf("Attempt : %s failed due to: %s", attempts, e1.getMessage());
}
attempts ++;
}
e.printStackTrace();
System.exit(1);
}
return Optional.empty();
}
```
But I'm still getting the same error.
Any kind of help will be very appreciated.