[driver.singularity.version](https://www.nomadproject.io/docs/drivers/external/singularity.html#driver-singularity-version) is [hard-coded](https://github.com/sylabs/nomad-driver-singularity/blob/master/cmd/driver/main.go#L31). Let's ask Singularity for version please: `singularity version`. Note that version string may be something like this: `3.4.2+ds2`.