locking seems to work in or out of the .proto file

example/Makefile

@@ -8,11 +8,10 @@ vet:
 	@GO111MODULE=off go vet
 
 build:
-	rm -f fruit.newsort.pb.go
 	GO111MODULE=off go build
 
 auto:
-	../autogenpb --proto fruit.proto --package main
+	../autogenpb --proto fruit.proto --package main --mutex
 
 goimports:
 	goimports -w *.go

sort.go

@@ -191,7 +191,7 @@ func (pf *File) appendUnique(w io.Writer, blah *MsgName, names map[string]string
 	var LOCK string = pf.Bases.Lockname
 
 	if argv.Mutex {
-		LOCK = pf.Bases.Name + ".Lock"
+		LOCK = pf.Bases.Lockname
 	} else {
 		LOCK = "all.Lock"
 	}