Terraform: use each.value inside herodoc string - amazon-web-services

Question

I'm trying to deploy four lambdas with their triggers.
The goal is not to repeat code blocks, so I'm using for_each so that a cloudwatch_event_rule is created for each lambda (I create them in pairs, "start" and "stop").
Everything is working OK except for one thing, I can not place each.value inside a herodoc string. This value will be the ARN of the Medialive channel, and I need to use the correct one each time I create a new event rule.
Using a the variable with the ARN there will not do, since it will create two event "start" rules with the same ARN (same for the "stop" rules).
Can this be achieved?
My code (I added "///// THIS IS NOT WORKING" where the problem is, for clarity):
locals {
lambda_start = {
"Newrelic_Start_${var.channel_name_1}" = {string = "${var.channel_arn_1}"},
"Newrelic_Start_${var.channel_name_2}" = {string = "${var.channel_arn_2}"},
}
lambda_stop = {
"Newrelic_Stop_${var.channel_name_1}" = {string = "${var.channel_arn_1}"},
"Newrelic_Stop_${var.channel_name_2}" = {string = "${var.channel_arn_2}"},
}
}
resource "aws_lambda_function" "lambda_starts" {
for_each = local.lambda_start
filename = "Archive_Start.zip"
function_name = each.key
role = "arn:aws:iam::${var.acc_id}:role/iam_for_lambda"
handler = "main.lambda_handler"
source_code_hash = filebase64sha256("Archive_Start.zip")
runtime = "python3.9"
architectures = ["x86_64"]
timeout = 60
}
resource "aws_lambda_function" "lambda_stops" {
for_each = local.lambda_stop
filename = "Archive_Stop.zip"
function_name = each.key
role = "arn:aws:iam::${var.acc_id}:role/iam_for_lambda"
handler = "main.lambda_handler"
source_code_hash = filebase64sha256("Archive_Stop.zip")
runtime = "python3.9"
architectures = ["x86_64"]
timeout = 60
}
# START 1
resource "aws_cloudwatch_event_rule" "console-1" {
for_each = local.lambda_start
name = each.key
event_pattern = <<EOF
{
"source": ["aws.medialive"],
"detail-type": ["AWS API Call via CloudTrail"],
"detail": {
"eventSource": ["medialive.amazonaws.com"],
"eventName": ["StartChannel"],
"responseElements": {
"arn": [{
"prefix":"${each.value}" ///// THIS IS NOT WORKING
}]
}
}
}
EOF
}
resource "aws_cloudwatch_event_target" "start" {
rule = aws_cloudwatch_event_rule.console-1[each.key].name
target_id = "lambda_starts"
for_each = local.lambda_start
arn = aws_lambda_function.lambda_starts[each.key].arn
}
resource "aws_lambda_permission" "allow_cloudwatch_to_call_lambda_starts" {
statement_id = "AllowExecutionFromCloudWatch"
action = "lambda:InvokeFunction"
for_each = local.lambda_start
function_name = aws_lambda_function.lambda_starts[each.key].function_name
principal = "events.amazonaws.com"
source_arn = aws_cloudwatch_event_rule.console-1[each.key].arn
}
#STOP 1
resource "aws_cloudwatch_event_rule" "console-stop-1" {
for_each = local.lambda_stop
name = each.key
event_pattern = <<EOF
{
"source": ["aws.medialive"],
"detail-type": ["AWS API Call via CloudTrail"],
"detail": {
"eventSource": ["medialive.amazonaws.com"],
"eventName": ["StopChannel"],
"responseElements": {
"arn": [{
"prefix": "${each.value}" ///// THIS IS NOT WORKING
}]
}
}
}
EOF
}
resource "aws_cloudwatch_event_target" "stop" {
rule = aws_cloudwatch_event_rule.console-stop-1[each.key].name
target_id = "lambda_stops"
for_each = local.lambda_stop
arn = aws_lambda_function.lambda_stops[each.key].arn
}
resource "aws_lambda_permission" "allow_cloudwatch_to_call_lambda_stops" {
statement_id = "AllowExecutionFromCloudWatch"
action = "lambda:InvokeFunction"
for_each = local.lambda_stop
function_name = aws_lambda_function.lambda_stops[each.key].function_name
principal = "events.amazonaws.com"
source_arn = aws_cloudwatch_event_rule.console-stop-1[each.key].arn
}
This is the error I get from the code above:
│ Error: Invalid template interpolation value
│
│ on main.tf line 163, in resource "aws_cloudwatch_event_rule" "console-stop-1":
│ 154: event_pattern = <<EOF
│ 155: {
│ 156: "source": ["aws.medialive"],
│ 157: "detail-type": ["AWS API Call via CloudTrail"],
│ 158: "detail": {
│ 159: "eventSource": ["medialive.amazonaws.com"],
│ 160: "eventName": ["StopChannel"],
│ 161: "responseElements": {
│ 162: "arn": [{
│ 163: "prefix": "${each.value}"
│ 164: }]
│ 165: }
│ 166: }
│ 167: }
│ 168: EOF
│ ├────────────────
│ │ each.value is object with 1 attribute "string"
│
│ Cannot include the given value in a string template: string required.
Any help will be appreciated