whatcanGOwrong

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

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+# 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

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+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

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+create table tasks (
+  id serial primary key,
+  description text not null
+);