At least in the following file, all *Callable functions return a future: https://github.com/awslabs/aws-sdk-cpp/blob/master/aws-cpp-sdk-s3/include/aws/s3/S3Cli

At least in the following file, all *Callable functions return a future: https://github.com/awslabs/aws-sdk-cpp/blob/master/aws-cpp-sdk-s3/include/aws/s3/S3Client.h https://github.com/awslabs/aws-sdk-cpp/blob/master/aws-cpp-s...