Move NullReader from nomad to util package.

util/util.go

@@ -0,0 +1,10 @@
+package util
+
+// NullReader is a struct that implements the io.Reader interface and returns nothing when reading
+// from it.
+type NullReader struct{}
+
+func (r NullReader) Read(_ []byte) (int, error) {
+	// An empty select blocks forever.
+	select {}
+}