json in heredoc in bash script alongwith variable substitution

heredoc_json.bash

_BUCKET_NAME="foo.example.com"

_POLICY=$(cat <<EOT
{
  "Version":"2012-10-17",
  "Statement":[{
    "Sid":"PublicReadForGetBucketObjects",
    "Effect":"Allow",
    "Principal": "*",
    "Action":["s3:GetObject"],
    "Resource":["arn:aws:s3:::${_BUCKET_NAME}/*"]
  }]
}
EOT
)

echo ${_POLICY}