golang.org/x/net v0.21.0: websocket.Handler, websocket.Message

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify golang.org/x/net/websocket in pkg:golang/golang.org/x/net@v0.21.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/net@v0.21.0
Demonstrate these symbols/APIs:
  - golang.org/x/net/websocket.Handler
  - golang.org/x/net/websocket.Message

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:9eb66ae9b8f9293ceb2b4e8a558408d5c51fd8773b86361284bbfbedbfda53c2","contract":["websocket.Handler wraps an HTTP handler function to serve WebSocket connections and echoes messages via websocket.Message.Send and websocket.Message.Receive","websocket.Message.Receive returns io.EOF or an error when the peer connection is closed"],"goal":"verify golang.org/x/net/websocket in pkg:golang/golang.org/x/net@v0.21.0","kind":"HOW","packages":["pkg:golang/golang.org/x/net@v0.21.0"],"schemaVersion":1,"symbols":["golang.org/x/net/websocket.Handler","golang.org/x/net/websocket.Message"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/net@v0.21.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/net@v0.21.0","symbols":["golang.org/x/net/websocket.Handler","golang.org/x/net/websocket.Message"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22.0

require golang.org/x/net v0.21.0

golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=

package main

import (
	"fmt"
	"log"
	"net/http/httptest"

	"golang.org/x/net/websocket"
)

func echoHandler(ws *websocket.Conn) {
	var msg string
	for {
		err := websocket.Message.Receive(ws, &msg)
		if err != nil {
			break
		}
		err = websocket.Message.Send(ws, msg)
		if err != nil {
			break
		}
	}
}

func main() {
	server := httptest.NewServer(websocket.Handler(echoHandler))
	defer server.Close()

	wsURL := "ws://" + server.Listener.Addr().String()
	ws, err := websocket.Dial(wsURL, "", "http://localhost/")
	if err != nil {
		log.Fatalf("failed to dial websocket: %v", err)
	}
	defer ws.Close()

	sendMsg := "hello websocket"
	if err := websocket.Message.Send(ws, sendMsg); err != nil {
		log.Fatalf("failed to send message: %v", err)
	}

	var recvMsg string
	if err := websocket.Message.Receive(ws, &recvMsg); err != nil {
		log.Fatalf("failed to receive message: %v", err)
	}

	fmt.Printf("Sent: %s, Received: %s\n", sendMsg, recvMsg)
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/net/websocket in pkg:golang/golang.org/x/net@v0.21.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/net@v0.21.0"
  ],
  "symbols": [
    "golang.org/x/net/websocket.Handler",
    "golang.org/x/net/websocket.Message"
  ]
}

package main

import (
	"errors"
	"fmt"
	"io"
	"net/http/httptest"
	"os"

	"golang.org/x/net/websocket"
)

func main() {
	// Assertion 1: websocket.Handler wraps an HTTP handler function to serve WebSocket connections and echoes messages via websocket.Message.Send and websocket.Message.Receive
	{
		handler := websocket.Handler(func(ws *websocket.Conn) {
			var msg string
			for {
				err := websocket.Message.Receive(ws, &msg)
				if err != nil {
					break
				}
				if err := websocket.Message.Send(ws, "echo:"+msg); err != nil {
					break
				}
			}
		})

		server := httptest.NewServer(handler)
		defer server.Close()

		wsURL := "ws://" + server.Listener.Addr().String()
		ws, err := websocket.Dial(wsURL, "", "http://localhost/")
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: dial error: %v\n", err)
			os.Exit(1)
		}

		sendMsg := "ping"
		if err := websocket.Message.Send(ws, sendMsg); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: send error: %v\n", err)
			os.Exit(1)
		}

		var recvMsg string
		if err := websocket.Message.Receive(ws, &recvMsg); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: receive error: %v\n", err)
			os.Exit(1)
		}

		if recvMsg != "echo:ping" {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: expected 'echo:ping', got %q\n", recvMsg)
			os.Exit(1)
		}

		ws.Close()
	}

	// Assertion 2: websocket.Message.Receive returns io.EOF or an error when the peer connection is closed
	{
		server := httptest.NewServer(websocket.Handler(func(ws *websocket.Conn) {
			// Immediately close connection from server side
			ws.Close()
		}))
		defer server.Close()

		wsURL := "ws://" + server.Listener.Addr().String()
		ws, err := websocket.Dial(wsURL, "", "http://localhost/")
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: dial error: %v\n", err)
			os.Exit(1)
		}
		defer ws.Close()

		var msg string
		err = websocket.Message.Receive(ws, &msg)
		if err == nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected error/EOF on closed connection, got nil\n")
			os.Exit(1)
		}
		if !errors.Is(err, io.EOF) && err.Error() == "" {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: unexpected empty error\n")
			os.Exit(1)
		}
	}

	fmt.Println("All contract assertions passed.")
}