Moving the Duration wrapper to it's own package to break import loops.

duration/duration.go

@@ -0,0 +1,20 @@
+package duration
+
+import "time"
+
+// Duration just wraps time.Duration
+type Duration struct {
+	time.Duration
+}
+
+// UnmarshalTOML parses the duration from the TOML config file
+func (d *Duration) UnmarshalTOML(b []byte) error {
+	dur, err := time.ParseDuration(string(b[1 : len(b)-1]))
+	if err != nil {
+		return err
+	}
+
+	d.Duration = dur
+
+	return nil
+}