pkg: hide it by moving to _pkg.dev

The idea here is to preserve the history of `dev` branch development and its
code when merging with the `master`. Later this code could be moved into the
masters code where appropriate.

_pkg.dev/wire/util/io/io.go

@@ -0,0 +1,17 @@
+package fileutils
+
+import (
+	"os"
+)
+
+// UpdateFile appends a byte slice to a file
+func UpdateFile(filename string, data []byte) error {
+
+	f, err := os.OpenFile(filename, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
+
+	dataWNewline := append(data, []byte("\n")...)
+
+	_, err = f.Write(dataWNewline)
+	err = f.Close()
+	return err
+}