We know the conversation [1].
Please update the page [2] about workspace option, like below:
data "terraform_remote_state" "foo" {
backend = "gcs"
workspace = terraform.workspace
config = {
bucket = "terraform-state"
prefix = "prod"
}
}
–
[1] https://github.com/hashicorp/terraform/issues/17153
[2] https://www.terraform.io/docs/backends/types/gcs.html