I am working on a company project and trying to upload a file to an S3 bucket in AWS. In our AWS kubernetes cluster, we annotate pod/service kube2iam role to authenticate without AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. I deployed a grpc server with kube2iam annotation. But when I tried to upload file using boto3 in grpc server, it says access denied. Anyone could help ?

Here is part of the server I deployed:

kind: Service
metadata:
  annotations:
    external-dns.alpha.kubernetes.io/hostname: <host_name>
    flux.weave.works/antecedent: baiflow:helmrelease/<release_name>
    iam.amazonaws.com/role: <kube2iam role>
    service.beta.kubernetes.io/aws-load-balancer-internal: "true"