hashicorp nomad .. why my app is not connecting to the database (Postgres , golang api) provider="nomad"

Question

Help required.. I tried in many ways but unfortunately app is not connecting to the database. DB_CONN is the env variable that app is expecting

service provider is nomad. so it must be a simple service discovery. Created two groups in same job file,infact I tried differently as well but it did not work.

variable "datacenters" {
  description = "A list of datacenters in the region which are eligible for task placement."
  type        = list(string)
  default     = ["dc1"]
}

variable "region" {
  description = "The region where the job should be placed."
  type        = string
  default     = "global"
}

variable "postgres_db" {
  description = "Postgres DB name"
  default     = "vehicle_master_bd"
}

variable "postgres_user" {
  description = "Postgres DB User"
  default     = "postgres"
}

variable "postgres_password" {
  description = "Postgres DB Password"
  default     = "postgres"
}

# Begin Job Spec
job "cres-vehicleMaster" {
  type        = "service"
  region      = var.region
  datacenters = var.datacenters
  group "db" {
    network {
      port "db" {
        to = 5432
      }
    }

    task "postgres" {
      driver = "docker"

      meta {
        service = "database"
      }
      service {
        name     = "database"
        port     = "db"
        provider = "nomad"
      }
      config {
        image = "postgres"
        ports = ["db"]
      }
      resources {
        cpu    = 500
        memory = 500
      }
      env {

        POSTGRES_DB       = var.postgres_db
        POSTGRES_USER     = var.postgres_user
        POSTGRES_PASSWORD = var.postgres_password
      }
    }
  }
  group "vehicleMaster-api" {
    count = 1
    network {
      port "api" {
        to = 50080
      }
    }

    restart {
      attempts = 2
      interval = "30m"
      delay    = "15s"
      mode     = "fail"
    }

    task "vehicleMaster-api" {
      driver = "docker"
      service {
        name     = "vehicleMaster-api"
        tags     = ["vehicleMaster", "RESTAPI"]
        port     = "api"
        provider = "nomad"
      }
      template {
        data        = <<EOH
{{ range nomadService "database" }}
DB_CONN="host={{ .Address }} port={{ .Port }} user=${var.postgres_user} password=${var.postgres_password} dbname=${var.postgres_db} sslmode=disable"
{{ end }}
EOH
        destination = "local/env.txt"
        env         = true
      }
      env {
        // DB_CONN = "host=127.0.0.1 port=5432 user=postgres password=postgres dbname=vehicle_master_bd sslmode=disable"
        // DB_CONN = "host=${NOMAD_IP_postgres} port=${NOMAD_PORT_postgres} user=${var.postgres_user} password=${var.postgres_password} dbname=${var.postgres_db} sslmode=disable"
        PORT    = "50080"
      }
      config {
        image = "jpalaparthi/vehiclemaster:v0.0.3"
        ports = ["api"]
      }
      resources {
        cpu    = 500 # 500 MHz
        memory = 512 # 256MB
      }
    }
  }
}