Added welcome messages to discord bot

bots/discord/OnGuildMemberAdd.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/bwmarrin/discordgo"
+)
+
+// Channels
+const welcomeChannel = "420600996268474368"
+const enChannel = "134910939140063232"
+const jpChannel = "334016470474424322"
+
+// Emoji
+const ramFive = ":ramFive:418520880511975426"
+const remFive = ":remFive:403671154553782275"
+
+// OnGuildMemberAdd is called every time a user joins the server.
+func OnGuildMemberAdd(session *discordgo.Session, event *discordgo.GuildMemberAdd) {
+	fmt.Println(event.Member.User.Username + " just joined!")
+
+	msg, err := session.ChannelMessageSend(welcomeChannel, fmt.Sprintf(
+		"**Welcome** %s!\n\nPlease introduce yourself in <#%s>.\n\n日本人は <#%s> で自己紹介して下さい！",
+		event.Member.User.Mention(),
+		enChannel,
+		jpChannel,
+	))
+
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	err = session.MessageReactionAdd(welcomeChannel, msg.ID, ramFive)
+
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	err = session.MessageReactionAdd(welcomeChannel, msg.ID, remFive)
+
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+}