curl --request GET \
  --url https://test.deribit.com/api/v2/public/subscribe \
  --header 'Content-Type: application/json' \
  --data '
{
  "jsonrpc": "2.0",
  "id": 3600,
  "method": "public/subscribe",
  "params": {
    "channels": [
      "deribit_price_index.btc_usd"
    ]
  }
}
'

{
  "jsonrpc": "2.0",
  "id": 4235,
  "result": [
    "deribit_price_index.btc_usd"
  ]
}