noCopy implements sync.Locker (#1216)

noCopy is used by -copylocks checker from `go vet`.
see golang/go#8005 (comment) for details.
but it doesn't work from Go 1.11, because of golang/go@c2eba53 and golang/go#26165
-copylock now works with structs that implement sync.Locker.
So, noCopy should implement sync.Locker.

utils.go

@@ -790,6 +790,12 @@ type noCopy struct{}
 // Lock is a no-op used by -copylocks checker from `go vet`.
 func (*noCopy) Lock() {}
 
+// Unlock is a no-op used by -copylocks checker from `go vet`.
+// noCopy should implement sync.Locker from Go 1.11
+// https://github.com/golang/go/commit/c2eba53e7f80df21d51285879d51ab81bcfbf6bc
+// https://github.com/golang/go/issues/26165
+func (*noCopy) Unlock() {}
+
 // atomicBool is a wrapper around uint32 for usage as a boolean value with
 // atomic access.
 type atomicBool struct {

utils_test.go

@@ -228,7 +228,9 @@ func TestAtomicBool(t *testing.T) {
 		t.Fatal("Expected value to be false")
 	}
 
-	ab._noCopy.Lock() // we've "tested" it ¯\_(ツ)_/¯
+	// we've "tested" them ¯\_(ツ)_/¯
+	ab._noCopy.Lock()
+	defer ab._noCopy.Unlock()
 }
 
 func TestAtomicError(t *testing.T) {