--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgo/go/internal/poll/fcntl_js.go	Mon May 25 07:50:57 2020 +0900
@@ -0,0 +1,14 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build js,wasm
+
+package poll
+
+import "syscall"
+
+// fcntl not supported on js/wasm
+func fcntl(fd int, cmd int, arg int) (int, error) {
+	return 0, syscall.ENOSYS
+}