feat: use TB.Setenv on Go 1.17

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

internal/testutil/env.go

@@ -9,15 +9,6 @@ import (
 // Licensed under the MIT license
 // Copyright (c) 2017 Canonical Ltd.
 
-// Setenv sets an environment variable to a temporary value for the
-// duration of the test.
-//
-// At the end of the test (see "Deferred execution" in the package docs), the
-// environment variable is returned to its original value.
-func Setenv(t *testing.T, name, val string) {
-	setenv(t, name, val, true)
-}
-
 // Unsetenv unsets an environment variable for the duration of a test.
 func Unsetenv(t *testing.T, name string) {
 	setenv(t, name, "", false)

internal/testutil/env_go1_16.go

@@ -0,0 +1,22 @@
+//go:build !go1.17
+// +build !go1.17
+
+package testutil
+
+import (
+	"os"
+	"testing"
+)
+
+// Based on https://github.com/frankban/quicktest/blob/577841610793d24f99e31cc2c0ef3a541fefd7c7/patch.go#L34-L64
+// Licensed under the MIT license
+// Copyright (c) 2017 Canonical Ltd.
+
+// Setenv sets an environment variable to a temporary value for the
+// duration of the test.
+//
+// At the end of the test (see "Deferred execution" in the package docs), the
+// environment variable is returned to its original value.
+func Setenv(t *testing.T, name, val string) {
+	setenv(t, name, val, true)
+}

internal/testutil/env_go1_17.go

@@ -0,0 +1,18 @@
+//go:build go1.17
+// +build go1.17
+
+package testutil
+
+import (
+	"testing"
+)
+
+// Setenv sets an environment variable to a temporary value for the
+// duration of the test.
+//
+// This shim can be removed once support for Go <1.17 is dropped.
+func Setenv(t *testing.T, name, val string) {
+	t.Helper()
+
+	t.Setenv(name, val)
+}