Bash in docker:dind?

The following bash script get executed fine in a python image but it failed in docker:dind image since docker:dind does not include bash. The error message was

./src/scripts/ line 18: syntax error: unexpected “(”

I tried to install bash using the following command below but that didn’t help

- apk update -qy && apk add -y --no-cache bash

here is my bash script

set -e
set -u
role_arn=AWS_DEPLOYMENT_ROLE_ARN session_name="{CI_BUILD_ID}-date +%Y%m%d"

kts=( $(
aws sts assume-role
–role-arn “$role_arn”
–role-session-name “$session_name”
–query ‘Credentials.[AccessKeyId,SecretAccessKey,SessionToken]’
–output text
) )