whatcanGOwrong

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

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+# Examples
+
+* chat is a command line chat program using listen/notify.
+* todo is a command line todo list that demonstrates basic CRUD actions.
+* url_shortener contains a simple example of using pgx in a web context.
+* [Tern](https://github.com/jackc/tern) is a migration tool that uses pgx.
+* [The Pithy Reader](https://github.com/jackc/tpr) is a RSS aggregator that uses pgx.

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)
+	}
+}

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

@@ -0,0 +1,67 @@
+# Description
+
+This is a sample todo list implemented using pgx as the connector to a
+PostgreSQL data store.
+
+# Usage
+
+Create a PostgreSQL database and run structure.sql into it to create the
+necessary data schema.
+
+Example:
+
+    createdb todo
+    psql todo < structure.sql
+
+Build todo:
+
+    go build
+
+## 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 todo:
+
+    export PGDATABASE=todo
+    ./todo list
+
+Or you can prefix the todo execution with the environment variables:
+
+    PGDATABASE=todo ./todo list
+
+## Add a todo item
+
+    ./todo add 'Learn go'
+
+## List tasks
+
+    ./todo list
+
+## Update a task
+
+    ./todo update 1 'Learn more go'
+
+## Delete a task
+
+    ./todo remove 1
+
+# Example Setup and Execution
+
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ createdb todo
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ psql todo < structure.sql
+    Expanded display is used automatically.
+    Timing is on.
+    CREATE TABLE
+    Time: 6.363 ms
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ go build
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ export PGDATABASE=todo
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo list
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo add 'Learn Go'
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo list
+    1. Learn Go
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo update 1 'Learn more Go'
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo list
+    1. Learn more Go
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo remove 1
+    jack@hk-47~/dev/go/src/github.com/jackc/pgx/examples/todo$ ./todo list

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

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"strconv"
+
+	"github.com/jackc/pgx/v4"
+)
+
+var conn *pgx.Conn
+
+func main() {
+	var err error
+	conn, err = pgx.Connect(context.Background(), os.Getenv("DATABASE_URL"))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Unable to connection to database: %v\n", err)
+		os.Exit(1)
+	}
+
+	if len(os.Args) == 1 {
+		printHelp()
+		os.Exit(0)
+	}
+
+	switch os.Args[1] {
+	case "list":
+		err = listTasks()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable to list tasks: %v\n", err)
+			os.Exit(1)
+		}
+
+	case "add":
+		err = addTask(os.Args[2])
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable to add task: %v\n", err)
+			os.Exit(1)
+		}
+
+	case "update":
+		n, err := strconv.ParseInt(os.Args[2], 10, 32)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable convert task_num into int32: %v\n", err)
+			os.Exit(1)
+		}
+		err = updateTask(int32(n), os.Args[3])
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable to update task: %v\n", err)
+			os.Exit(1)
+		}
+
+	case "remove":
+		n, err := strconv.ParseInt(os.Args[2], 10, 32)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable convert task_num into int32: %v\n", err)
+			os.Exit(1)
+		}
+		err = removeTask(int32(n))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Unable to remove task: %v\n", err)
+			os.Exit(1)
+		}
+
+	default:
+		fmt.Fprintln(os.Stderr, "Invalid command")
+		printHelp()
+		os.Exit(1)
+	}
+}
+
+func listTasks() error {
+	rows, _ := conn.Query(context.Background(), "select * from tasks")
+
+	for rows.Next() {
+		var id int32
+		var description string
+		err := rows.Scan(&id, &description)
+		if err != nil {
+			return err
+		}
+		fmt.Printf("%d. %s\n", id, description)
+	}
+
+	return rows.Err()
+}
+
+func addTask(description string) error {
+	_, err := conn.Exec(context.Background(), "insert into tasks(description) values($1)", description)
+	return err
+}
+
+func updateTask(itemNum int32, description string) error {
+	_, err := conn.Exec(context.Background(), "update tasks set description=$1 where id=$2", description, itemNum)
+	return err
+}
+
+func removeTask(itemNum int32) error {
+	_, err := conn.Exec(context.Background(), "delete from tasks where id=$1", itemNum)
+	return err
+}
+
+func printHelp() {
+	fmt.Print(`Todo pgx demo
+
+Usage:
+
+  todo list
+  todo add task
+  todo update task_num item
+  todo remove task_num
+
+Example:
+
+  todo add 'Learn Go'
+  todo list
+`)
+}

go/pkg/mod/github.com/jackc/pgx/v4@v4.18.3/examples/todo/structure.sql

@@ -0,0 +1,4 @@
+create table tasks (
+  id serial primary key,
+  description text not null
+);

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

@@ -0,0 +1,33 @@
+# Description
+
+This is a sample REST URL shortener service implemented using pgx as the connector to a PostgreSQL data store.
+
+# Usage
+
+Create a PostgreSQL database and run structure.sql into it to create the necessary data schema.
+
+Configure the database connection with `DATABASE_URL` or standard PostgreSQL (`PG*`) environment variables or
+
+Run main.go:
+
+```
+go run main.go
+```
+
+## Create or Update a Shortened URL
+
+```
+curl -X PUT -d 'http://www.google.com' http://localhost:8080/google
+```
+
+## Get a Shortened URL
+
+```
+curl http://localhost:8080/google
+```
+
+## Delete a Shortened URL
+
+```
+curl -X DELETE http://localhost:8080/google
+```

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

@@ -0,0 +1,98 @@
+package main
+
+import (
+	"context"
+	"io/ioutil"
+	"net/http"
+	"os"
+
+	"github.com/jackc/pgx/v4"
+	"github.com/jackc/pgx/v4/log/log15adapter"
+	"github.com/jackc/pgx/v4/pgxpool"
+	log "gopkg.in/inconshreveable/log15.v2"
+)
+
+var db *pgxpool.Pool
+
+func getUrlHandler(w http.ResponseWriter, req *http.Request) {
+	var url string
+	err := db.QueryRow(context.Background(), "select url from shortened_urls where id=$1", req.URL.Path).Scan(&url)
+	switch err {
+	case nil:
+		http.Redirect(w, req, url, http.StatusSeeOther)
+	case pgx.ErrNoRows:
+		http.NotFound(w, req)
+	default:
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+	}
+}
+
+func putUrlHandler(w http.ResponseWriter, req *http.Request) {
+	id := req.URL.Path
+	var url string
+	if body, err := ioutil.ReadAll(req.Body); err == nil {
+		url = string(body)
+	} else {
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := db.Exec(context.Background(), `insert into shortened_urls(id, url) values ($1, $2)
+	on conflict (id) do update set url=excluded.url`, id, url); err == nil {
+		w.WriteHeader(http.StatusOK)
+	} else {
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+	}
+}
+
+func deleteUrlHandler(w http.ResponseWriter, req *http.Request) {
+	if _, err := db.Exec(context.Background(), "delete from shortened_urls where id=$1", req.URL.Path); err == nil {
+		w.WriteHeader(http.StatusOK)
+	} else {
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+	}
+}
+
+func urlHandler(w http.ResponseWriter, req *http.Request) {
+	switch req.Method {
+	case "GET":
+		getUrlHandler(w, req)
+
+	case "PUT":
+		putUrlHandler(w, req)
+
+	case "DELETE":
+		deleteUrlHandler(w, req)
+
+	default:
+		w.Header().Add("Allow", "GET, PUT, DELETE")
+		w.WriteHeader(http.StatusMethodNotAllowed)
+	}
+}
+
+func main() {
+	logger := log15adapter.NewLogger(log.New("module", "pgx"))
+
+	poolConfig, err := pgxpool.ParseConfig(os.Getenv("DATABASE_URL"))
+	if err != nil {
+		log.Crit("Unable to parse DATABASE_URL", "error", err)
+		os.Exit(1)
+	}
+
+	poolConfig.ConnConfig.Logger = logger
+
+	db, err = pgxpool.ConnectConfig(context.Background(), poolConfig)
+	if err != nil {
+		log.Crit("Unable to create connection pool", "error", err)
+		os.Exit(1)
+	}
+
+	http.HandleFunc("/", urlHandler)
+
+	log.Info("Starting URL shortener on localhost:8080")
+	err = http.ListenAndServe("localhost:8080", nil)
+	if err != nil {
+		log.Crit("Unable to start web server", "error", err)
+		os.Exit(1)
+	}
+}

go/pkg/mod/github.com/jackc/pgx/v4@v4.18.3/examples/url_shortener/structure.sql

@@ -0,0 +1,4 @@
+create table shortened_urls (
+  id text primary key,
+  url text not null
+);