In v0.10.4, A data race condition has been detected when running tests with -race flag.

I suspect the following is occurring from this PR (#490 ):

• runtime.AnalyzeTypeAddr() is being called in both initDecoder and initEncoder.
• Although using sync.Once, since initEncoderOnce and initDecoderOnce are separate variables, concurrent calls to initEncoder and initDecoder result in race conditions in runtime.AnalyzeTypeAddr() operations.

In our project, tests that simultaneously use json.Marshal and json.Unmarshal have become flaky.