Closes #74

This fix makes sure that generated message IDs via SetMessageID() are truly random and unique

msg.go

@@ -357,12 +357,12 @@ func (m *Msg) SetMessageID() {
 	if err != nil {
 		hn = "localhost.localdomain"
 	}
-	ct := time.Now().Unix()
+	ct := time.Now().UnixNano()
 	r := rand.New(rand.NewSource(ct))
-	rn := r.Int()
+	rn := r.Int63()
 	pid := os.Getpid()
-
-	mid := fmt.Sprintf("%d.%d.%d@%s", pid, rn, ct, hn)
+	cts := fmt.Sprintf("%d", ct)
+	mid := fmt.Sprintf("%d.%d.%s@%s", pid, rn, cts[:15], hn)
 	m.SetMessageIDWithValue(mid)
 }
 

msg_test.go

@@ -695,6 +695,26 @@ func TestMsg_SetMessageIDWithValue(t *testing.T) {
 	}
 }
 
+// TestMsg_SetMessageIDRandomness tests the randomness of Msg.SetMessageID methods
+func TestMsg_SetMessageIDRandomness(t *testing.T) {
+	var mids []string
+	for i := 0; i < 100; i++ {
+		m := NewMsg()
+		m.SetMessageID()
+		mid := m.GetGenHeader(HeaderMessageID)
+		mids = append(mids, mid[0])
+	}
+	c := make(map[string]int)
+	for i := range mids {
+		c[mids[i]]++
+	}
+	for k, v := range c {
+		if v > 1 {
+			t.Errorf("MessageID randomness not give. MessageID %q was generated %d times", k, v)
+		}
+	}
+}
+
 // TestMsg_FromFormat tests the FromFormat and EnvelopeFrom methods for the Msg object
 func TestMsg_FromFormat(t *testing.T) {
 	tests := []struct {