Hi@akhtar,
Terraform has one keyword named route. It allows us to create a route in our routing table. You can see the below-given example.
resource "aws_route_table" "table" {
  vpc_id = "${aws_vpc.main.id}"
route {
    cidr_block = "0.0.0.0/0"
    gateway_id = "${aws_internet_gateway.gw.id}"
  }
}