Bot: Added Run(); updated examples

README.md

@@ -49,6 +49,38 @@ This example demonstrates the PreHandler feature of the state library.
 PreHandler calls all handlers that are registered (separately from the session),
 calling them before the state is updated.
 
+### Bare Minimum Bot
+
+The least amount of code for a basic ping-pong bot. It's similar to Serenity's
+Discord bot example in the README.
+
+```go
+package main
+
+import (
+	"os"
+
+	"github.com/diamondburned/arikawa/v2/bot"
+	"github.com/diamondburned/arikawa/v2/gateway"
+)
+
+func main() {
+	bot.Run(os.Getenv("DISCORD_TOKEN"), &Bot{},
+		func(ctx *bot.Context) error {
+			ctx.HasPrefix = bot.NewPrefix("!")
+		},
+	)
+}
+
+type Bot struct {
+	Ctx *bot.Context
+}
+
+func (b *Bot) Ping(*gateway.MessageCreateEvent) (string, error) {
+	return "Pong!", nil
+}
+```
+
 ### [Advanced Bot](https://github.com/diamondburned/arikawa/tree/v2/_example/advanced_bot)
 
 A complex example demonstrating the reflect-based command router that's

_example/advanced_bot/main.go

@@ -19,7 +19,7 @@ func main() {
 
 	commands := &Bot{}
 
-	wait, err := bot.Start(token, commands, func(ctx *bot.Context) error {
+	bot.Run(token, commands, func(ctx *bot.Context) error {
 		ctx.HasPrefix = bot.NewPrefix("!", "~")
 		ctx.EditableCommands = true
 
@@ -32,18 +32,4 @@ func main() {
 
 		return nil
 	})
-
-	if err != nil {
-		log.Fatalln(err)
-	}
-
-	log.Println("Bot started")
-
-	// As of this commit, wait() will block until SIGINT or fatal. The past
-	// versions close on call, but this one will block.
-	// If for some reason you want the Cancel() function, manually make a new
-	// context.
-	if err := wait(); err != nil {
-		log.Fatalln("Gateway fatal error:", err)
-	}
 }

bot/ctx.go

@@ -147,7 +147,15 @@ func Start(
 	token string, cmd interface{},
 	opts func(*Context) error) (wait func() error, err error) {
 
-	s, err := state.New("Bot " + token)
+	if token == "" {
+		return nil, errors.New("token is not given")
+	}
+
+	if !strings.HasPrefix(token, "Bot ") {
+		token = "Bot " + token
+	}
+
+	s, err := state.New(token)
 	if err != nil {
 		return nil, errors.Wrap(err, "failed to create a dgo session")
 	}
@@ -188,6 +196,22 @@ func Start(
 	}, nil
 }
 
+// Run starts the bot, prints a message into the console, and blocks until
+// SIGINT. "Bot" is prepended into the token automatically, similar to Start.
+// The function will call os.Exit(1) on an initialization or cleanup error.
+func Run(token string, cmd interface{}, opts func(*Context) error) {
+	wait, err := Start(token, cmd, opts)
+	if err != nil {
+		log.Fatalln("failed to start:", err)
+	}
+
+	log.Println("Bot is running.")
+
+	if err := wait(); err != nil {
+		log.Fatalln("cleanup error:", err)
+	}
+}
+
 // Wait blocks until SIGINT.
 func Wait() {
 	sigs := make(chan os.Signal, 1)