From b21bf1031aa3278718f987369e11f8a098f9338b Mon Sep 17 00:00:00 2001
From: Alec Thomas <alec@swapoff.org>
Date: Wed, 19 Feb 2020 13:19:52 +1100
Subject: [PATCH] Support interpolating "$env".

Fixes #57.
---
 kong.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kong.go b/kong.go
index 713c337..64cd407 100644
--- a/kong.go
+++ b/kong.go
@@ -153,6 +153,9 @@ func (k *Kong) interpolateValue(value *Value, vars Vars) (err error) {
 		"default": value.Default,
 		"enum":    value.Enum,
 	})
+	if value.Tag.Env != "" {
+		vars["env"] = value.Tag.Env
+	}
 	if value.Help, err = interpolate(value.Help, vars); err != nil {
 		return fmt.Errorf("help for %s: %s", value.Summary(), err)
 	}