14564:3350c94fe6b7 tip
Add the following test to encoding/gob package:

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
    }
}

go test -race says:

WARNING: DATA RACE
Read by goroutine 69:
  encoding/gob.RegisterName()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type.go:729 +0xde
  encoding/gob.Register()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type.go:785 +0x202
  encoding/gob.func·023()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type_test.go:201 +0x4d

Previous write by goroutine 68:
  encoding/gob.RegisterName()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type.go:738 +0x26d
  encoding/gob.Register()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type.go:785 +0x202
  encoding/gob.func·023()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type_test.go:201 +0x4d

Goroutine 69 (running) created at:
  encoding/gob.TestParallel()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type_test.go:214 +0xac
  testing.tRunner()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/testing/testing.go:301 +0x86

Goroutine 68 (running) created at:
  encoding/gob.TestParallel()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/encoding/gob/type_test.go:214 +0xac
  testing.tRunner()
      /usr/local/google/home/dvyukov/go_prefetch/src/pkg/testing/testing.go:301 +0x86