encoding/gob: add test case for issue 4214.

See http://code.google.com/p/go/issues/detail?id=4214

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/6619068

src/pkg/encoding/gob/type_test.go

@@ -5,6 +5,7 @@
 package gob
 
 import (
+	"bytes"
 	"reflect"
 	"testing"
 )
@@ -192,3 +193,30 @@ func TestRegistrationNaming(t *testing.T) {
 		}
 	}
 }
+
+func TestStressParallel(t *testing.T) {
+	type T2 struct{ A int }
+	c := make(chan bool)
+	const N = 10
+	for i := 0; i < N; i++ {
+		go func() {
+			p := new(T2)
+			Register(p)
+			b := new(bytes.Buffer)
+			enc := NewEncoder(b)
+			err := enc.Encode(p)
+			if err != nil {
+				t.Error("encoder fail:", err)
+			}
+			dec := NewDecoder(b)
+			err = dec.Decode(p)
+			if err != nil {
+				t.Error("decoder fail:", err)
+			}
+			c <- true
+		}()
+	}
+	for i := 0; i < N; i++ {
+		<-c
+	}
+}