Add generic reader

pkg/io/reader.go

@@ -0,0 +1,14 @@
+package io
+
+// Reader is a generic reader. When generic is ready, interface{} will be replaced
+// with a generic type and will provide type safety.
+type Reader interface {
+	Read() (interface{}, error)
+}
+
+// ReaderFunc is a proxy type to make easier for users to implement Reader
+type ReaderFunc func() (interface{}, error)
+
+func (f ReaderFunc) Read() (interface{}, error) {
+	return f()
+}