can not get specific log from records

I have fluent-bit deployed in k8s with the go plugin, but we noticed some specific logs are lost.

Here is the pod's log:

{"level":"debug","ts":1625627314150.1467,"caller":"xservice/callback.go:179","msg":"api call done","app":"test","appBuildHost":"runner-x","appBuildTime":"2021-07-06 10:14:06","appGoVersion":"go1.15","appGitTag":"v0.6.0_2021-07-06_10-14-06","appGitVersion":"30333326","Resp":"task_id:1628888882647513000 data:{x_id:6108888888888787 xList:{rn:\"rn:xt:x/64888888889070\" timestamp:{seconds:1625627313 nanos:21238000} x_id:2020092191 status:FINISHED amount:{amount:1} x_list:{amount:{amount:1} x:{rn:\"rn:xx:y/59578888888885733\" x_owner:{user_rn:\"rn:user:legacy-user/1688850\" xx_qq_rn:\"rn:xx:xx/58033951876352146:qq/59600811175680000\" display_name:{language:\"zh-CN\" text:\"张\"}} type:EXTERNAL display_name:{language:\"zh-CN\" text:\"测试 Mall\"}} external_xx_info:\"{\\\"Data\\\":{\\\"XInCent\\\":1,\\\"CreateTime\\\":1625627313,\\\"Cent\\\":1,\\\"ETime\\\":1625627313,\\\"ErrorCode\\\":null,\\\"ErrorDescription\\\":null,\\\"Status\\\":\\\"Success\\\"},\\\"ID\\\":\\\"73b7cb2ad93f\\\",\\\"NotifyTime\\\":1625627313,\\\"NotifyType\\\":\\\"XResult\\\",\\\"XServiceID\\\":1712788888888888889,\\\"XNumber\\\":46766078888888888875}\"}}}","x-trace-id":"da488888888888758893429","x-span-id":"7188888888833","x-parent-id":"388888888886"}

In `FLBPluginFlushCtx`, I tried to print all records but found no messages like `api call done` in fluent-bit's output.

```go
//export FLBPluginFlushCtx
func FLBPluginFlushCtx(ctx, data unsafe.Pointer, length C.int, tag *C.char) int {
// Type assert context back into the original type for the Go variable
// cfgContext := output.FLBPluginGetContext(ctx).(map[string]string)

dec := output.NewDecoder(data, int(length))

messages := make(map[string][]string)

for {
ret, _, record := output.GetRecord(dec)
if ret != 0 {
break
}

fbTag := fmt.Sprintf("%s", C.GoString(tag))

for k, v := range record {
fmt.Printf("tag: %s, record: \"%s\": %v, \n", fbTag, k, v)
}
}

return output.FLB_OK
}
```