feat: add and use a duration helper type

autonat.go

@@ -75,5 +75,7 @@ type AutoNATThrottleConfig struct {
 
 	// Interval specifies how frequently this node should reset the
 	// global/peer dialback limits.
-	Interval string
+	//
+	// When unset, this defaults to 1 minute.
+	Interval Duration `json:",omitempty"`
 }

types.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"encoding/json"
+	"time"
 )
 
 // Strings is a helper type that (un)marshals a single string to/from a single
@@ -39,3 +40,22 @@ func (o Strings) MarshalJSON() ([]byte, error) {
 
 var _ json.Unmarshaler = (*Strings)(nil)
 var _ json.Marshaler = (*Strings)(nil)
+
+// Duration wraps time.Duration to provide json serialization and deserialization.
+//
+// NOTE: the zero value encodes to an empty string.
+type Duration time.Duration
+
+func (d *Duration) UnmarshalText(text []byte) error {
+	dur, err := time.ParseDuration(string(text))
+	*d = Duration(dur)
+	return err
+}
+
+func (d Duration) MarshalText() ([]byte, error) {
+	return []byte(time.Duration(d).String()), nil
+}
+
+func (d Duration) String() string {
+	return time.Duration(d).String()
+}

types_test.go

@@ -3,8 +3,40 @@ package config
 import (
 	"encoding/json"
 	"testing"
+	"time"
 )
 
+func TestDuration(t *testing.T) {
+	out, err := json.Marshal(Duration(time.Second))
+	if err != nil {
+		t.Fatal(err)
+
+	}
+	expected := "\"1s\""
+	if string(out) != expected {
+		t.Fatalf("expected %s, got %s", expected, string(out))
+	}
+	var d Duration
+	err = json.Unmarshal(out, &d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if time.Duration(d) != time.Second {
+		t.Fatal("expected a second")
+	}
+	type Foo struct {
+		D Duration `json:",omitempty"`
+	}
+	out, err = json.Marshal(new(Foo))
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected = "{}"
+	if string(out) != expected {
+		t.Fatal("expected omitempty to omit the duration")
+	}
+}
+
 func TestOneStrings(t *testing.T) {
 	out, err := json.Marshal(Strings{"one"})
 	if err != nil {