Fix:(issue_1272) Generic flag not set from env

flag_test.go

@@ -166,6 +166,10 @@ func TestFlagsFromEnv(t *testing.T) {
 				if !reflect.DeepEqual(ctx.Value(test.flag.Names()[0]), test.output) {
 					t.Errorf("ex:%01d expected %q to be parsed as %#v, instead was %#v", i, test.input, test.output, ctx.Value(test.flag.Names()[0]))
 				}
+				if !f.IsSet() {
+					t.Errorf("Flag %s not set", f.Names()[0])
+				}
+
 				return nil
 			},
 		}