update stream.go

[vearne]

增加限制json Marsharl递归层级，来防止循环引用，引起的栈溢出

[codecov]

Codecov Report

Merging #332 into master will increase coverage by 0.02%.
The diff coverage is 31.81%.

@@ Coverage Diff @@ ## master #332 +/- ## ========================================= + Coverage 81.48% 81.5% +0.02%  ========================================= Files 41 41 Lines 5013 5035 +22 ========================================= + Hits 4085 4104 +19  + Misses 807 803 -4  - Partials 121 128 +7

Impacted Files	Coverage Δ
config.go	89.36% <ø> (ø)	⬆️
reflect_array.go	75% <0%> (-2.59%)	⬇️
reflect_slice.go	93.44% <0%> (-3.17%)	⬇️
reflect_map.go	85.78% <0%> (-1.72%)	⬇️
reflect_struct_encoder.go	87.5% <0%> (-1.49%)	⬇️
pool.go	100% <100%> (ø)	⬆️
stream.go	82.72% <50%> (-3.28%)	⬇️
reflect_struct_decoder.go	48.74% <0%> (+1.67%)	⬆️

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[vearne]

处理循环引用所导致的栈溢出问题
类似下面的场景
http://vearne.cc/archives/1464