feat(scanner): add option to use fsnotify based scan watcher (#232)

* First cut at fsnotify support. Tested on Linux.

* Fixed bug in logging.

* Fixed lint issues.

* Added new scan watcher option to README.md

* Inverted conditional and dedented following code as per PR discussion.

* Changed command line switch and error return on ExecuteWatch() as per GH comments.

* Scan watcher: Removed scan at first start. Modified watcher to set a 10 second timer and then process in bulk.

Co-authored-by: Brian Doherty <brian@hplaptop.dohertyfamily.me>

server/server.go

@@ -296,6 +296,7 @@ func (s *Server) StartHTTP(listenAddr string, tlsCert string, tlsKey string) (Fu
 		Addr:         listenAddr,
 		Handler:      s.router,
 		ReadTimeout:  5 * time.Second,
+		ReadHeaderTimeout:  5 * time.Second,
 		WriteTimeout: 80 * time.Second,
 		IdleTimeout:  60 * time.Second,
 	}
@@ -338,6 +339,16 @@ func (s *Server) StartScanTicker(dur time.Duration) (FuncExecute, FuncInterrupt)
 		}
 }
 
+func (s *Server) StartScanWatcher() (FuncExecute, FuncInterrupt) {
+	return func() error {
+			log.Printf("starting job 'scan watcher'\n")
+			return s.scanner.ExecuteWatch()
+		}, func(_ error) {
+			// stop job
+			s.scanner.CancelWatch()
+		}
+}
+
 func (s *Server) StartJukebox() (FuncExecute, FuncInterrupt) {
 	return func() error {
 			log.Printf("starting job 'jukebox'\n")