$ cat prometheus.conf
global:
  evaluation_interval: 15s
  labels: {env: qa1}
  scrape_interval: 15s

scrape_configs:
- file_sd_configs:
  - names: [/tmp/test-job-with-labels.yml]
  job_name: target_group_with_labels

$ cat /tmp/test-job-with-labels.yml
- targets: ['localhost:9100']
  labels:
    foo: bar

$ ./prometheus -config.file=prometheus.conf -storage.local.path="/home/ubuntu/metrics"