Error: Unsupported attribute

╷
│ Error: Unsupported attribute
│
│   on main.tf line 15, in resource "aws_db_instance" "my_mariadb_instance":
│   15:   db_subnet_group_name =  module.vpc.my-vpc-name.database_subnet_group
│     ├────────────────
│     │ module.vpc is a object, known only after apply
│
│ This object does not have an attribute named "my-vpc-name".
╵

See also

• terraform plan: [ -refresh-only | -lock=false | -target | -var-file | will be created | --help], Terraform plan errors, Terraform plan examples, Terraform plan execution errors, (known after apply)