Echo

import json, urllib.request

# GET
resp = urllib.request.urlopen("https://catastrophic.io/echo?foo=bar&baz=1")
print(json.loads(resp.read()))

# POST with a body
data = json.dumps({"key": "value"}).encode()
req = urllib.request.Request(
    "https://catastrophic.io/echo",
    data=data,
    headers={"Content-Type": "application/json", "X-My-Header": "hello"},
)
print(json.loads(urllib.request.urlopen(req).read()))

// GET
const r1 = await fetch("https://catastrophic.io/echo?foo=bar&baz=1");
console.log(await r1.json());

// POST
const r2 = await fetch("https://catastrophic.io/echo", {
    method: "POST",
    headers: { "Content-Type": "application/json", "X-My-Header": "hello" },
    body: JSON.stringify({ key: "value" }),
});
console.log(await r2.json());

package main

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

func main() {
    // GET
    r1, _ := http.Get("https://catastrophic.io/echo?foo=bar&baz=1")
    b1, _ := io.ReadAll(r1.Body)
    fmt.Println(string(b1))
    r1.Body.Close()

    // POST
    body := strings.NewReader(`{"key":"value"}`)
    req, _ := http.NewRequest("POST", "https://catastrophic.io/echo", body)
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("X-My-Header", "hello")
    r2, _ := http.DefaultClient.Do(req)
    b2, _ := io.ReadAll(r2.Body)
    fmt.Println(string(b2))
    r2.Body.Close()
}

// Cargo.toml: reqwest    = { version = "0.12", features = ["blocking", "json"] }
//             serde_json = "1"
fn main() -> Result<(), Box> {
    let client = reqwest::blocking::Client::new();

    // GET
    let r1 = client.get("https://catastrophic.io/echo?foo=bar&baz=1").send()?;
    println!("{}", r1.text()?);

    // POST
    let r2 = client
        .post("https://catastrophic.io/echo")
        .header("X-My-Header", "hello")
        .json(&serde_json::json!({ "key": "value" }))
        .send()?;
    println!("{}", r2.text()?);
    Ok(())
}

// Java 11+ HttpClient
import java.net.URI;
import java.net.http.*;

public class Echo {
    public static void main(String[] args) throws Exception {
        var client = HttpClient.newHttpClient();

        // GET
        var r1 = client.send(
            HttpRequest.newBuilder(URI.create("https://catastrophic.io/echo?foo=bar&baz=1")).build(),
            HttpResponse.BodyHandlers.ofString());
        System.out.println(r1.body());

        // POST
        var r2 = client.send(
            HttpRequest.newBuilder(URI.create("https://catastrophic.io/echo"))
                .header("Content-Type", "application/json")
                .header("X-My-Header", "hello")
                .POST(HttpRequest.BodyPublishers.ofString("{\"key\":\"value\"}"))
                .build(),
            HttpResponse.BodyHandlers.ofString());
        System.out.println(r2.body());
    }
}

// .NET 6+
using System.Text;
using var client = new HttpClient();

// GET
Console.WriteLine(await client.GetStringAsync("https://catastrophic.io/echo?foo=bar&baz=1"));

// POST — use HttpRequestMessage to attach arbitrary headers
var req = new HttpRequestMessage(HttpMethod.Post, "https://catastrophic.io/echo");
req.Headers.Add("X-My-Header", "hello");
req.Content = new StringContent("{\"key\":\"value\"}", Encoding.UTF8, "application/json");
var r2 = await client.SendAsync(req);
Console.WriteLine(await r2.Content.ReadAsStringAsync());

require "net/http"
require "json"

# GET
r1 = Net::HTTP.get_response(URI("https://catastrophic.io/echo?foo=bar&baz=1"))
puts r1.body

# POST
uri = URI("https://catastrophic.io/echo")
req = Net::HTTP::Post.new(uri)
req["Content-Type"] = "application/json"
req["X-My-Header"] = "hello"
req.body = JSON.dump(key: "value")
r2 = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |h| h.request(req) }
puts r2.body

# GET — inspect what headers PowerShell adds automatically
$r = Invoke-WebRequest -Uri 'https://catastrophic.io/echo?foo=bar'
$r.Content | ConvertFrom-Json | Select-Object method, headers

# POST with a body
$r = Invoke-WebRequest -Uri 'https://catastrophic.io/echo' `
    -Method POST `
    -ContentType 'application/json' `
    -Body '{"key":"value"}'
$r.Content | ConvertFrom-Json