Use errgroup for a cleaner and no-deadlock implementation of AddNodes

go.mod

@@ -1,10 +1,11 @@
 module meow.tf/astra/gavalink
 
 require (
-	github.com/bwmarrin/discordgo v0.20.3 // indirect
+	github.com/bwmarrin/discordgo v0.20.3
 	github.com/foxbot/gavalink v0.0.0-20181105223750-6252b1245300
 	github.com/gorilla/websocket v1.4.0
 	github.com/valyala/fastjson v1.4.1
+	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a
 )
 
 go 1.13

go.sum

@@ -8,3 +8,5 @@ github.com/valyala/fastjson v1.4.1 h1:hrltpHpIpkaxll8QltMU8c3QZ5+qIiCL8yKqPFJI/y
 github.com/valyala/fastjson v1.4.1/go.mod h1:nV6MsjxL2IMJQUoHDIrjEI7oLyeqK6aBD7EFWPsvP8o=
 golang.org/x/crypto v0.0.0-20181030102418-4d3f4d9ffa16 h1:y6ce7gCWtnH+m3dCjzQ1PCuwl28DDIc3VNnvY29DlIA=
 golang.org/x/crypto v0.0.0-20181030102418-4d3f4d9ffa16/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a h1:DcqTD9SDLc+1P/r1EmRBwnVsrOwW+kk2vWf9n+1sGhs=
+golang.org/x/sync v0.0.0-20201207232520-09787c993a3a/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=

lavalink.go

@@ -1,7 +1,9 @@
 package gavalink
 
 import (
+	"context"
 	"errors"
+	"golang.org/x/sync/errgroup"
 	"log"
 	"net/http"
 	"os"
@@ -65,41 +67,29 @@ func (l *Lavalink) AddNodes(nodeConfigs ...NodeConfig) error {
 		Timeout: 60 * time.Second,
 	}
 
-	wg := &sync.WaitGroup{}
-
-	errCh := make(chan error)
+	eg, ctx := errgroup.WithContext(context.Background())
 
 	for _, c := range nodeConfigs {
-		n := &Node{
-			config:  c,
-			manager: l,
-			client:  client,
-		}
+		eg.Go(func() error {
+			n := &Node{
+				config:  c,
+				manager: l,
+				client:  client,
+			}
 
-		wg.Add(1)
-
-		go func(n *Node, wg *sync.WaitGroup, errCh chan error) {
-			defer wg.Done()
-
-			err := n.open()
+			err := n.open(ctx)
 
 			if err != nil {
-				errCh <- err
-				return
+				return err
 			}
 
 			l.nodes = append(l.nodes, n)
-		}(n, wg, errCh)
+
+			return nil
+		})
 	}
 
-	wg.Wait()
-
-	select {
-	case err := <-errCh:
-		return err
-	default:
-		return nil
-	}
+	return eg.Wait()
 }
 
 // RemoveNode removes a node from the manager

node.go

@@ -1,6 +1,7 @@
 package gavalink
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"github.com/valyala/fastjson"
@@ -15,16 +16,21 @@ import (
 
 // NodeConfig configures a Lavalink Node
 type NodeConfig struct {
+	// Node identifier (uuid, hostname, etc)
+	Identifier string
+
 	// REST is the host where Lavalink's REST server runs
 	//
 	// This value is expected without a trailing slash, e.g. like
 	// `http://localhost:2333`
 	REST string
+
 	// WebSocket is the host where Lavalink's WebSocket server runs
 	//
 	// This value is expected without a trailing slash, e.g. like
 	// `http://localhost:8012`
 	WebSocket string
+
 	// Password is the expected Authorization header for the Node
 	Password string
 }
@@ -68,7 +74,7 @@ type FrameStats struct {
 }
 
 // Opens the connection to the Lavalink server
-func (node *Node) open() error {
+func (node *Node) open(ctx context.Context) error {
 	header := http.Header{}
 
 	header.Set("User-Agent", gavalinkUserAgent())
@@ -92,7 +98,7 @@ func (node *Node) open() error {
 		header.Set("Capabilities", strings.Join(v, ";"))
 	}
 
-	ws, resp, err := websocket.DefaultDialer.Dial(node.config.WebSocket, header)
+	ws, resp, err := websocket.DefaultDialer.DialContext(ctx, node.config.WebSocket, header)
 
 	if err != nil {
 		return err
@@ -136,7 +142,7 @@ func (node *Node) listen() {
 		if err != nil {
 			Log.Println(err)
 			// try to reconnect
-			oerr := node.open()
+			oerr := node.open(context.Background())
 
 			if oerr != nil {
 				Log.Println("node", node.config.WebSocket, "failed and could not reconnect, destroying.", err, oerr)

player.go

@@ -184,7 +184,9 @@ func (player *Player) Forward(sessionID string, event VoiceServerUpdate) error {
 func (player *Player) ChangeNode(node *Node) error {
 	player.node = node
 
-	player.Forward(player.sessionID, player.lastVoiceServerUpdate)
+	if err := player.Forward(player.sessionID, player.lastVoiceServerUpdate); err != nil {
+		return err
+	}
 
 	return player.PlayAt(player.track, player.position, 0)
 }