mount: use pooled goroutine instead of round-robin

fix https://github.com/chrislusf/seaweedfs/issues/2263

go.mod

@@ -57,7 +57,7 @@ require (
 	github.com/pquerna/cachecontrol v0.1.0
 	github.com/prometheus/client_golang v1.11.0
 	github.com/rcrowley/go-metrics v0.0.0-20190826022208-cac0b30c2563 // indirect
-	github.com/seaweedfs/fuse v1.1.8
+	github.com/seaweedfs/fuse v1.1.9
 	github.com/seaweedfs/goexif v1.0.2
 	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e
 	github.com/spaolacci/murmur3 v1.1.0 // indirect

go.sum

@@ -629,6 +629,8 @@ github.com/samuel/go-zookeeper v0.0.0-20190923202752-2cc03de413da/go.mod h1:gi+0
 github.com/sean-/seed v0.0.0-20170313163322-e2103e2c3529/go.mod h1:DxrIzT+xaE7yg65j358z/aeFdxmN0P9QXhEzd20vsDc=
 github.com/seaweedfs/fuse v1.1.8 h1:YFSDPotG4uhQzV7ooDUvQ8BRVy5rM1XCFPJAmAsZz68=
 github.com/seaweedfs/fuse v1.1.8/go.mod h1:+PP6WlkrRUG6KPE+Th2EX5To/PjHaFsvqg/UgQ39aj8=
+github.com/seaweedfs/fuse v1.1.9 h1:5nLBDlD9OgUI5hleKOtsCz8L1Q5kxgx3EUKTmQ1GNqk=
+github.com/seaweedfs/fuse v1.1.9/go.mod h1:+PP6WlkrRUG6KPE+Th2EX5To/PjHaFsvqg/UgQ39aj8=
 github.com/seaweedfs/goexif v1.0.2 h1:p+rTXYdQ2mgxd+1JaTrQ9N8DvYuw9UH9xgYmJ+Bb29E=
 github.com/seaweedfs/goexif v1.0.2/go.mod h1:MrKs5LK0HXdffrdCZrW3OIMegL2xXpC6ThLyXMyjdrk=
 github.com/secsy/goftp v0.0.0-20190720192957-f31499d7c79a h1:C6IhVTxNkhlb0tlCB6JfHOUv1f0xHPK7V8X4HlJZEJw=