lesson 11

lesson_11/cancellation/go.mod

@@ -0,0 +1,3 @@
+module cancellation
+
+go 1.22.2

lesson_11/cancellation/main.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+)
+
+func main() {
+	abort := make(chan struct{})
+
+	go func() {
+		var b = make([]byte, 1)
+
+		for {
+			os.Stdin.Read(b)
+
+			if b[0] == 'Q' || b[0] == 'q' {
+				abort <- struct{}{}
+				return
+			}
+		}
+	}()
+
+	fmt.Println("Commencing countdown. Press 'Q' to abort.")
+
+	tick := time.Tick(1 * time.Second)
+
+	for countdown := 10; countdown > 0; countdown-- {
+		fmt.Println(countdown)
+
+		select {
+		case <-tick:
+			fmt.Println("...")
+		case <-abort:
+			fmt.Println("Launch aborted!")
+			return
+		}
+	}
+
+	launch()
+}
+
+func launch() {
+	fmt.Println("Lift off!")
+}

lesson_11/cancellation_complex/go.mod

@@ -0,0 +1,3 @@
+module cancellation_complex
+
+go 1.22.2

lesson_11/cancellation_complex/main.go

@@ -0,0 +1,71 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"sync"
+	"time"
+)
+
+var done = make(chan struct{})
+var wg sync.WaitGroup
+
+func main() {
+	go func() {
+		os.Stdin.Read(make([]byte, 1)) // read a single byte
+		close(done)
+	}()
+
+	fmt.Println("Press enter to cancel the tasks.")
+
+	completion := make(chan int)
+
+	for i := 0; i < 5; i++ {
+		if cancelled() {
+			fmt.Println("Main loop cancelled!")
+			break
+		}
+
+		wg.Add(1)
+		go longRunningTask(i, completion)
+	}
+
+	go func() {
+		wg.Wait()
+		close(completion)
+	}()
+
+	for result := range completion {
+		fmt.Printf("Task %d completed\n", result)
+	}
+
+	fmt.Println("Main function completed.")
+}
+
+func cancelled() bool {
+	select {
+	case <-done:
+		return true
+	default:
+		return false
+	}
+}
+
+func longRunningTask(id int, completion chan<- int) {
+	defer wg.Done()
+
+	for i := 0; i < 3; i++ {
+		select {
+		case <-done:
+			fmt.Printf("Task %d cancelled during execution!\n", id)
+			return
+		default:
+			// Simulate some work with a sleep
+			fmt.Printf("Task %d working... %d\n", id, i)
+			time.Sleep(1 * time.Second)
+		}
+	}
+
+	completion <- id
+	fmt.Printf("Task %d completed!\n", id)
+}

lesson_11/chat_client/go.mod

@@ -0,0 +1,3 @@
+module chat_client
+
+go 1.22.2

lesson_11/chat_client/main.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"bufio"
+	"crypto/tls"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+)
+
+func main() {
+	// Define command-line arguments
+	serverAddr := flag.String("server", "localhost:8000", "server address in the format ip:port")
+	flag.Parse()
+
+	conn, err := makeConn(*serverAddr)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close()
+
+	fmt.Printf("Connected to %s\n", *serverAddr)
+
+	// Channel to signal when the server connection is closed
+	done := make(chan struct{})
+
+	// Start a goroutine to read messages from the server and print them
+	go readMessages(conn, done)
+
+	// Read input from the user and send it to the server
+	go sendMessage(conn, done)
+
+	// Wait for the done signal indicating the server connection is closed
+	<-done
+	fmt.Println("Disconnected from server.")
+}
+
+// makeConn establishes a TLS connection to the server.
+func makeConn(serverAddr string) (*tls.Conn, error) {
+	conf := &tls.Config{
+		InsecureSkipVerify: true, // Insecure, should be used with caution
+	}
+
+	return tls.Dial("tcp", serverAddr, conf)
+}
+
+func readMessages(conn *tls.Conn, done chan<- struct{}) {
+	scanner := bufio.NewScanner(conn)
+	for scanner.Scan() {
+		fmt.Println(scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		log.Println("Error reading from server:", err)
+	}
+	close(done)
+}
+
+func sendMessage(conn *tls.Conn, done chan<- struct{}) {
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		text := scanner.Text()
+
+		if text == "/exit" {
+			fmt.Println("Exiting chat...")
+			conn.Close()
+			close(done)
+			return
+		}
+
+		_, err := fmt.Fprintln(conn, text)
+		if err != nil {
+			log.Println("Error sending to server:", err)
+			break
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Println("Error reading from stdin:", err)
+	}
+}

lesson_11/chat_server/cert.pem

@@ -0,0 +1,31 @@
+-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----

lesson_11/chat_server/go.mod

@@ -0,0 +1,10 @@
+module chat_server
+
+go 1.22.2
+
+require (
+	github.com/fatih/color v1.17.0 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	golang.org/x/sys v0.18.0 // indirect
+)

lesson_11/chat_server/go.sum

@@ -0,0 +1,11 @@
+github.com/fatih/color v1.17.0 h1:GlRw1BRJxkpqUCBKzKOw098ed57fEsKeNjpTe3cSjK4=
+github.com/fatih/color v1.17.0/go.mod h1:YZ7TlrGPkiz6ku9fK3TLD/pl3CpsiFyu8N92HLgmosI=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
+github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
+github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
+github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWEY=
+github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
+golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
+golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

lesson_11/chat_server/key.pem

@@ -0,0 +1,52 @@
+-----BEGIN PRIVATE KEY-----
+MIIJQgIBADANBgkqhkiG9w0BAQEFAASCCSwwggkoAgEAAoICAQCYnSKui3dmcUuD
+joWZwJehxOFqLmI2U022lNP5T37OOiLEl02oGqnB//wt0OMnCLNvUAz0piCd5gGL
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+xVMGJ4zm9LOG/mIya36nhFHUW9tb2338lUot+gpYw5cCDHUGr4XlbRiyKSLvETAP
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+xi04d/VCFz6MHTeFI9WTJ/jtyjN7VA==
+-----END PRIVATE KEY-----