Golang 中的 zap.Logger 线程安全吗？

兴趣问。我在 GitHub 上发现了一个关于这个主题的 issue，有这样一个代码示例：

package main

import "github.com/uber-go/zap"

var logger zap.Logger

func main() {
    logger = zap.NewJSON()

    for i := 0; i < 800; i++ {
        go printer(i)
    }
}

func printer(i int) {
    logger.Info("Counting",
        zap.Int("i", i),
    )
}

这给出了（给定的）这种输出：

{"msg":"Counting","level":"info","ts":1469196244924860064,"fields":{"i":8}}
{"msg":"Counting","level":"info","ts":1469196244924867134,"fields":{"i":42}}
{"msg":"Counting","level":"info","ts":1469196244924866589,"fields":{"i":20}}
{"msg":"Counti{"msg":"Counting","level":"info","ts":1469196244924879429,"fields":{"i":21}}
ng","level":"info","ts":1469196244924870959,"fields":{"i":9}}
{"msg":"Counting","level":"info","ts":1469196244924879050,"fields":{"i":36}}
{"msg":"Counting","level":"info","ts":1469196244924873937,"fields":{"i":43}}
{"msg":"Counting","level":"info","ts":1469196244924904543,"fields":{"i":22}}
{"msg":"Counting","level":"info","ts":1469196244924910632,"fields":{"i":10}}
{"msg":"Counting","level":"info","ts":1469196244924916792,"fields":{"i":23}}
...

您可以在第 4 行看到叠加层。但显然问题几乎同时解决了。在所有运行中，此示例的更新版本会产生偶数列的输出：

package main

import "go.uber.org/zap"

var logger *zap.Logger

func main() {
    logger, _ = zap.NewProduction()

    for i := 0; i < 800; i++ {
        go printer(i)
    }
}

func printer(i int) {
    logger.Info("Counting",
        zap.Int("i", i),
    )
}