add support for duration flag

altsrc/flag.go

@@ -204,12 +204,16 @@ func (f *IntFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContex
 // ApplyInputSourceValue applies a Duration value to the flagSet if required
 func (f *DurationFlag) ApplyInputSourceValue(cCtx *cli.Context, isc InputSourceContext) error {
 	if f.set != nil && !(cCtx.IsSet(f.Name) || isEnvVarSet(f.EnvVars)) && isc.isSet(f.DurationFlag.Name) {
-		value, err := isc.Duration(f.DurationFlag.Name)
+		for _, name := range f.DurationFlag.Names() {
-		if err != nil {
+			if isc.isSet(name) {
-			return err
+				value, err := isc.Duration(name)
-		}
+				if err != nil {
-		for _, name := range f.Names() {
+					return err
-			_ = f.set.Set(name, value.String())
+				}
+				for _, n := range f.Names() {
+					_ = f.set.Set(n, value.String())
+				}
+			}
 		}
 	}
 	return nil

altsrc/flag_test.go

@@ -400,6 +400,19 @@ func TestIntApplyInputSourceMethodEnvVarSet(t *testing.T) {
 	refute(t, 12, c.Int("test"))
 }
 
+func TestDurationApplyInputSourceMethodSet_Alias(t *testing.T) {
+	tis := testApplyInputSource{
+		Flag:     NewDurationFlag(&cli.DurationFlag{Name: "test", Aliases: []string{"test_alias"}}),
+		FlagName: "test",
+		MapValue: 30 * time.Second,
+	}
+	c := runTest(t, tis)
+	expect(t, 30*time.Second, c.Duration("test_alias"))
+
+	c = runRacyTest(t, tis)
+	refute(t, 30*time.Second, c.Duration("test_alias"))
+}
+
 func TestDurationApplyInputSourceMethodSet(t *testing.T) {
 	tis := testApplyInputSource{
 		Flag:     NewDurationFlag(&cli.DurationFlag{Name: "test"}),