restructure inotify package and add some tests

internal/inotify/observer.go

@@ -0,0 +1,23 @@
+package inotify
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+func Observe(i *Inotify, triggerCh chan struct{}, dataCh chan []byte, errCh chan error) {
+	buf := make([]byte, 5*unix.SizeofInotifyEvent)
+
+	for {
+		n, errno := unix.Read(i.fd, buf)
+		if n == -1 {
+			errCh <- fmt.Errorf("reading from inotify fd: errno: %d", errno)
+			return
+		}
+		triggerCh <- struct{}{}
+		bufCopy := make([]byte, n)
+		copy(bufCopy, buf)
+		dataCh <- bufCopy
+	}
+}