bugfix: Delete put(c) HandleContext

[deepdarkness]

This method "engine.pool.Put(c)" may put c twice in pool, this is a bug may cause a request with no response and another response with more than one response body.

First put:

func (engine *Engine) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	c := engine.pool.Get().(*Context)
	c.writermem.reset(w)
	c.Request = req
	c.reset()
	engine.handleHTTPRequest(c)
	engine.pool.Put(c)
}

Second put:

func (engine *Engine) HandleContext(c *Context) {
	c.reset()
	engine.handleHTTPRequest(c)
	engine.pool.Put(c)
}

It may cause series problem, can return confusion response to use, Next request may take a using Context to response. Request Log:

[2018-09-29 19:51:21] method[POST] statusCode[200] remoteIP[----] requestId[8f6bafbe-b9af-43b8-956f-eed0ecfbe1e4] costTime[67.052ms] path[/front/v1/get/execQuery] ReqBody[{"RequestId":"8f6bafbe-b9af-43b8-956f-eed0ecfbe1e4","SubAccountUin":"----","Uin":"----","epoch":"ms","orgId":"-----etjgxtuw","query":"SELECT mean(\"free\") \n    FROM \"disk\"\n    WHERE time \u003e now() - 1h AND \"insId\" = 'IP_----'\n    GROUP BY time(5m)"}] RespBody[]

[2018-09-29 19:51:21] method[POST] statusCode[200] remoteIP[----] requestId[764b89a1-bc0b-4573-b625-40950baace32] costTime[49.432ms] path[/front/v1/get/execQuery] ReqBody[{"epoch":"ms","orgId":"-----etjgxtuw","query":"SELECT mean(\"used\") \n    FROM \"disk\"\n    WHERE time \u003e now() - 1h AND \"insId\" = 'IP_----'\n    GROUP BY time(5m)"}] RespBody[{"Response":{"RequestId":"764b89a1-bc0b-4573-b625-40950baace32","ResponseBody":"{\"results\":[{\"statement_id\":0,\"series\":[{\"name\":\"disk\",\"columns\":[\"time\",\"mean\"],\"values\":[[1538218200000,13094400],[1538218500000,13094400],[1538218800000,13094400],[1538219100000,13094400],[1538219400000,13094400],[1538219700000,13094400],[1538220000000,13094400],[1538220300000,13094400],[1538220600000,13094400],[1538220900000,13094400],[1538221200000,13094400],[1538221500000,13094400],[1538221800000,13094400]]}]}]}\n"}}{"Response":{"RequestId":"764b89a1-bc0b-4573-b625-40950baace32","ResponseBody":"{\"results\":[{\"statement_id\":0,\"series\":[{\"name\":\"disk\",\"columns\":[\"time\",\"mean\"],\"values\":[[1538218200000,196057271734.85715],[1538218500000,196057202688],[1538218800000,196057109435.73334],[1538219100000,196057034296.8889],[1538219400000,196056924433.06668],[1538219700000,196056770833.06668],[1538220000000,196056610816],[1538220300000,196056530807.46667],[1538220600000,196056445424.48486],[1538220900000,196056361398.85715],[1538221200000,196056234448.21335],[1538221500000,196056150971.73334],[1538221800000,196056091891.8095]]}]}]}\n"}}{"Response":{"RequestId":"764b89a1-bc0b-4573-b625-40950baace32","ResponseBody":"{\"results\":[{\"statement_id\":0,\"series\":[{\"name\":\"disk\",\"columns\":[\"time\",\"mean\"],\"values\":[[1538218200000,4435639539.809524],[1538218500000,4435708586.666667],[1538218800000,4435801838.933333],[1538219100000,4435876977.777778],[1538219400000,4435986841.6],[1538219700000,4436140441.6],[1538220000000,4436300458.666667],[1538220300000,4436380467.2],[1538220600000,4436465850.181818],[1538220900000,4436549875.809524],[1538221200000,4436676826.453333],[1538221500000,4436760302.933333],[1538221800000,4436819382.857142]]}]}]}\n"}}]

There is two ResponseBody in second resp but empty ResponseBody in first query. like second req stole from first req.

[codecov]

Codecov Report

Merging #1579 into master will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1579      +/-   ##
==========================================
+ Coverage   99.06%   99.11%   +0.05%     
==========================================
  Files          39       39              
  Lines        1929     1928       -1     
==========================================
  Hits         1911     1911              
+ Misses         14       13       -1     
  Partials        4        4

Impacted Files	Coverage Δ
gin.go	98.53% <ø> (+0.47%)	⬆️

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[thinkerou]

@deepdarkness please #1565 thanks your commit.

[appleboy]

#1565 merged.