From 0ecd272e23814bddc938ba6776c47e5f33df723e Mon Sep 17 00:00:00 2001
From: Alec Thomas <alec@swapoff.org>
Date: Tue, 14 Nov 2023 09:36:03 +1100
Subject: [PATCH] fix: use LookupEnv to check if envar is actually set

Fixes #389
---
 model.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/model.go b/model.go
index 793cf97..ae40672 100644
--- a/model.go
+++ b/model.go
@@ -368,9 +368,9 @@ func (v *Value) Reset() error {
 	v.Target.Set(reflect.Zero(v.Target.Type()))
 	if len(v.Tag.Envs) != 0 {
 		for _, env := range v.Tag.Envs {
-			envar := os.Getenv(env)
+			envar, ok := os.LookupEnv(env)
 			// Parse the first non-empty ENV in the list
-			if envar != "" {
+			if ok {
 				err := v.Parse(ScanFromTokens(Token{Type: FlagValueToken, Value: envar}), v.Target)
 				if err != nil {
 					return fmt.Errorf("%s (from envar %s=%q)", err, env, envar)