v3.6.0/examples/resources/random_password/resource.tf

resource "random_password" "password" {
  length           = 16
  special          = true
  override_special = "!#$%&*()-_=+[]{}<>:?"
}

resource "aws_db_instance" "example" {
  instance_class    = "db.t3.micro"
  allocated_storage = 64
  engine            = "mysql"
  username          = "someone"
  password          = random_password.password.result
}