fix errors collecting on multi-host

Signed-off-by: Artemiy Ryabinkov <getlag@ya.ru>

conn.go

@@ -467,8 +467,8 @@ func connect(config ConnConfig, connInfo *pgtype.ConnInfo) (c *Conn, err error)
 	}
 
 	errmsgs := make([]string, len(errs))
-	for _, err := range errs {
-		errmsgs = append(errmsgs, err.Error())
+	for i, err := range errs {
+		errmsgs[i] = err.Error()
 	}
 
 	return nil, errors.New(strings.Join(errmsgs, ";"))

examples/multihosts/README.md

@@ -0,0 +1,25 @@
+# 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 the standard PostgreSQL environment variables.
+
+* PGHOST - defaults to localhost
+* PGUSER - defaults to current OS user
+* PGPASSWORD - defaults to empty string
+* PGDATABASE - defaults to user name
+
+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

examples/multihosts/main.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"os"
+
+	"github.com/jackc/pgx"
+)
+
+var pool *pgx.ConnPool
+
+func main() {
+	config, err := pgx.ParseEnvLibpq()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Unable to parse environment:", err)
+		os.Exit(1)
+	}
+
+	pool, err = pgx.NewConnPool(pgx.ConnPoolConfig{ConnConfig: config})
+	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("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()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "Error acquiring connection:", err)
+		os.Exit(1)
+	}
+	defer pool.Release(conn)
+
+	conn.Listen("chat")
+
+	for {
+		notification, err := 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)
+	}
+}