I am trying to create a terraform code to run shell script and that output i like parse into variable on runtime to Parse in locals.

But locals unable to get shell script value, as it is executed first

locals {
  instance_config = jsondecode("${null_resource.execute_shell_script.result}")
}

resource "null_resource" "execute_shell_script" {
  provisioner "local-exec" {
    command     = "bash ${path.module}/shell_3.sh"
    interpreter = ["bash", "-c"]
  }
}

#!/bin/bash

echo "instance_config = {"

cluster="cluster1 cluster2"
cluster1_con="con1 con2 con3"
cluster2_con="con4 con5 con6"

for i in $cluster; do
    echo "    "$i" = ["
    con_var="${i}_con"
    con_values="${!con_var}"
    for node in $con_values; do
        echo "        "$node","
    done
    echo "    ]"
done

echo "}"