Do a large chunk of the move to go

This commit moves a huge chunk of the code to go. The TODO.md document
indicates what is left to be done.

internal/hostname/hostname.go

@@ -0,0 +1,32 @@
+// Package hostname provides hostname
+package hostname
+
+import (
+	"os"
+
+	"github.com/Showmax/go-fqdn"
+)
+
+// FQDN attempts to return the fully qualified domain name of the host system.
+// If an error occurs, may fall back to the empty string.
+func FQDN() string {
+
+	// try the hostname function
+	{
+		fqdn, err := fqdn.FqdnHostname()
+		if err == nil {
+			return fqdn
+		}
+	}
+
+	// fallback to os hostname
+	{
+		hostname, err := os.Hostname()
+		if err == nil {
+			return hostname
+		}
+	}
+
+	// use the empty string
+	return ""
+}