Run service in user root

Hi ,
I trying to run docker with user root

task "init_airflows" {
            driver = "docker"
            config {
                image = "apache/airflow:2.2.5"
                user = "root"

But I get an error

2022-10-27T15:50:54Z  Failed Validation  2 errors occurred:
        * failed to parse config: 
        * Invalid label: No argument or block type is named "user".

It is set on the same level as your config-block; not inside it.