whatcanGOwrong

go/pkg/mod/github.com/jackc/pgx/v4@v4.18.3/examples/chat/README.md

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+# Description
+
+This is a sample chat program implemented using PostgreSQL's listen/notify
+functionality with pgx.
+
+Start multiple instances of this program connected to the same database to chat
+between them.
+
+## Connection configuration
+
+The database connection is configured via DATABASE_URL and standard PostgreSQL environment variables (PGHOST, PGUSER, etc.)
+
+You can either export them then run chat:
+
+    export PGHOST=/private/tmp
+    ./chat
+
+Or you can prefix the chat execution with the environment variables:
+
+    PGHOST=/private/tmp ./chat

go/pkg/mod/github.com/jackc/pgx/v4@v4.18.3/examples/chat/main.go

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+package main
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/jackc/pgx/v4/pgxpool"
+)
+
+var pool *pgxpool.Pool
+
+func main() {
+	var err error
+	pool, err = pgxpool.Connect(context.Background(), os.Getenv("DATABASE_URL"))
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Unable to connect to database:", err)
+		os.Exit(1)
+	}
+
+	go listen()
+
+	fmt.Println(`Type a message and press enter.
+
+This message should appear in any other chat instances connected to the same
+database.
+
+Type "exit" to quit.`)
+
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		msg := scanner.Text()
+		if msg == "exit" {
+			os.Exit(0)
+		}
+
+		_, err = pool.Exec(context.Background(), "select pg_notify('chat', $1)", msg)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "Error sending notification:", err)
+			os.Exit(1)
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		fmt.Fprintln(os.Stderr, "Error scanning from stdin:", err)
+		os.Exit(1)
+	}
+}
+
+func listen() {
+	conn, err := pool.Acquire(context.Background())
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Error acquiring connection:", err)
+		os.Exit(1)
+	}
+	defer conn.Release()
+
+	_, err = conn.Exec(context.Background(), "listen chat")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Error listening to chat channel:", err)
+		os.Exit(1)
+	}
+
+	for {
+		notification, err := conn.Conn().WaitForNotification(context.Background())
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "Error waiting for notification:", err)
+			os.Exit(1)
+		}
+
+		fmt.Println("PID:", notification.PID, "Channel:", notification.Channel, "Payload:", notification.Payload)
+	}
+}