Correct some error handling, use package that provides useful stack traces

server/filesystem.go

@@ -4,9 +4,9 @@ import (
 	"bufio"
 	"bytes"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"github.com/gabriel-vasile/mimetype"
+	"github.com/pkg/errors"
 	"github.com/pterodactyl/wings/config"
 	"go.uber.org/zap"
 	"io"

server/server.go

@@ -1,9 +1,9 @@
 package server
 
 import (
-	"errors"
 	"fmt"
 	"github.com/patrickmn/go-cache"
+	"github.com/pkg/errors"
 	"github.com/pterodactyl/wings/api"
 	"github.com/pterodactyl/wings/config"
 	"github.com/remeh/sizedwaitgroup"