fix compile error for -tags=jsoniter

[junfengye]

add newencoder to fix compile error for -tags=jsoniter

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[codecov]

Codecov Report

Merging #1500 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1500   +/-   ##
=======================================
  Coverage   99.16%   99.16%           
=======================================
  Files          39       39           
  Lines        1914     1914           
=======================================
  Hits         1898     1898           
  Misses         13       13           
  Partials        3        3

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[thinkerou]

ref #694 LGTM