curl --request POST 'https://eth.rpc.novacula.io' \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: YOUR_API_KEY' \
  --data '{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}'

const response = await fetch("https://eth.rpc.novacula.io", {
  method: "POST",
  headers: { "Content-Type": "application/json", "x-api-key": "YOUR_API_KEY" },
  body: JSON.stringify({ jsonrpc: "2.0", id: 1, method: "eth_blockNumber", params: [] }),
});
console.log(await response.json());

import json
import urllib.request

request = urllib.request.Request(
    "https://eth.rpc.novacula.io",
    data=json.dumps({"jsonrpc": "2.0", "id": 1, "method": "eth_blockNumber", "params": []}).encode(),
    headers={"Content-Type": "application/json", "x-api-key": "YOUR_API_KEY"},
    method="POST",
)
with urllib.request.urlopen(request) as response:
    print(json.load(response))

package main

import (
    "fmt"
    "io"
    "net/http"
    "strings"
)

func main() {
    body := strings.NewReader("{\"jsonrpc\":\"2.0\",\"id\":1,\"method\":\"eth_blockNumber\",\"params\":[]}")
    req, err := http.NewRequest("POST", "https://eth.rpc.novacula.io", body)
    if err != nil { panic(err) }
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("x-api-key", "YOUR_API_KEY")
    res, err := http.DefaultClient.Do(req)
    if err != nil { panic(err) }
    defer res.Body.Close()
    data, err := io.ReadAll(res.Body)
    if err != nil { panic(err) }
    fmt.Println(string(data))
}