I use to connect to EC2 container instances following this steps, https://docs.aws.amazon.com/AmazonECS/latest/developerguide/instance-connect.html wondering how I can connect to FARGATE-managed container instances instead.
Looking on that issue on github https://github.com/aws/amazon-ecs-cli/issues/143 I think it's not possible to make docker exec from remote host into container on ECS Fargate. You can try to run ssh daemon and your main process in one container using e.g. systemd (https://docs.docker.com/config/containers/multi-service_container/) and connect to your container using SSH but generally it's not good idea in containers world.