Unable Connect to STS if using a VPC

[SolYs02]

Describe the bug

Same as #4301

Describe the bug
When I attempt to send an STS message from a Lambda function in a VPC, I encounter a timeout issue. I tried using the VPC Link, but it didn’t work.

This solution resolved the problem:

assumed_role = boto3.client( "sts", endpoint_url=f"https://sts.{os.environ['AWS_REGION']}.amazonaws.com", )

Expected Behavior
Successfully executed boto3's sts.get_caller_identity().

Current Behavior
Received a timeout error.

Reproduction Steps
Create a VPC without internet access, add an STS interface endpoint, and then attempt to call boto3's sts.get_caller_identity().

[tim-finnigan]

Thanks for reaching out. Please refer to this documentation: https://docs.aws.amazon.com/sdkref/latest/guide/feature-sts-regionalized-endpoints.html. Setting the AWS_STS_REGIONAL_ENDPOINTS environment variable or sts_regional_endpoints configuration to regional will force the boto3 to use regional rather than global endpoints when calling STS.