Trying to use a service account on my aws ec2 instance

OK.

That is probably expected - if you didn't supply any auth in the config then you'll need to set env_auth true. env is the general environment, so environment variables, config files or EC2 metadata server.

Sorry, I mis-understood your previous statement! Yes you need to set env_auth true if you want to use the metadata server.

Get AWS credentials from runtime (environment variables or EC2/ECS meta data if no env vars). Only applies if access_key_id and secret_access_key is blank.
Choose a number from below, or type in your own value
1 / Enter AWS credentials in the next step
\ "false"
2 / Get AWS credentials from the environment (env vars or IAM)
\ "true"
env_auth> 1