Volume data not persisting with Terraform

Hi,

I’m trying to achieve a setup whereby i can tear down a droplet and reattach it to a volume whenever i need to update code etc.

But after i re attach the volume to the droplet , all the data is gone. here is my config:

resource "digitalocean_volume" "main-api" {
	region = "lon1"
	name = "ms-vol-two"
	size = 2
	initial_filesystem_type = "ext4"
	description = "File storage for postgres"
}

resource "digitalocean_droplet" "main-api" {
	image = "docker-18-04"
	name = "main-api"
	region = "lon1"
	size = "512mb"
	private_networking = true
	ssh_keys = [
		var.ssh_fingerprint
	]
 ... etc

}

resource "digitalocean_volume_attachment" "main-api" {
	droplet_id = digitalocean_droplet.main-api.id
	volume_id = digitalocean_volume.main-api.id
}

When i SSH into the droplet i /mnt/ms_vol_two exists but has no data. I can create data there and it saves normally. But when i destroy the main-api droplet and then re run with terraform apply the droplet only has /mnt/ms_vol_two but the data is no longer there…? Thanks, Joe.