management server listener (#17)

Reviewed-on: #17
Co-authored-by: David Ashby <delta.mu.alpha@gmail.com>
Co-committed-by: David Ashby <delta.mu.alpha@gmail.com>

query/null.go

@@ -0,0 +1,11 @@
+package query
+
+import (
+	"git.yetaga.in/alazyreader/library/media"
+)
+
+type Null struct{}
+
+func (o *Null) GetByISBN(isbn string) (*media.Book, error) {
+	return nil, nil
+}