1 package main
2
3 import (
4 "bufio"
5 "context"
6 "fmt"
7 "os"
8
9 "github.com/jackc/pgx/v5/pgxpool"
10 )
11
12 var pool *pgxpool.Pool
13
14 func main() {
15 var err error
16 pool, err = pgxpool.New(context.Background(), os.Getenv("DATABASE_URL"))
17 if err != nil {
18 fmt.Fprintln(os.Stderr, "Unable to connect to database:", err)
19 os.Exit(1)
20 }
21
22 go listen()
23
24 fmt.Println(`Type a message and press enter.
25
26 This message should appear in any other chat instances connected to the same
27 database.
28
29 Type "exit" to quit.`)
30
31 scanner := bufio.NewScanner(os.Stdin)
32 for scanner.Scan() {
33 msg := scanner.Text()
34 if msg == "exit" {
35 os.Exit(0)
36 }
37
38 _, err = pool.Exec(context.Background(), "select pg_notify('chat', $1)", msg)
39 if err != nil {
40 fmt.Fprintln(os.Stderr, "Error sending notification:", err)
41 os.Exit(1)
42 }
43 }
44 if err := scanner.Err(); err != nil {
45 fmt.Fprintln(os.Stderr, "Error scanning from stdin:", err)
46 os.Exit(1)
47 }
48 }
49
50 func listen() {
51 conn, err := pool.Acquire(context.Background())
52 if err != nil {
53 fmt.Fprintln(os.Stderr, "Error acquiring connection:", err)
54 os.Exit(1)
55 }
56 defer conn.Release()
57
58 _, err = conn.Exec(context.Background(), "listen chat")
59 if err != nil {
60 fmt.Fprintln(os.Stderr, "Error listening to chat channel:", err)
61 os.Exit(1)
62 }
63
64 for {
65 notification, err := conn.Conn().WaitForNotification(context.Background())
66 if err != nil {
67 fmt.Fprintln(os.Stderr, "Error waiting for notification:", err)
68 os.Exit(1)
69 }
70
71 fmt.Println("PID:", notification.PID, "Channel:", notification.Channel, "Payload:", notification.Payload)
72 }
73 }
74
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