google-app-engine - 在 app.yaml 上指定了环境变量，但它没有在 main.go 上获取

Question

我已经在 app.yaml 中指定了我的环境变量，当我在我的本地机器上运行它时，它正在被获取，但是一旦我部署了它，它就不会获取它。

我是这样设置的:

application: some-application
version: 1
runtime: go
api_version: go1
threadsafe: true

handlers: 
- url: /.*
  script: main.go
  secure: always

env_variables: 
  ENVIRONMENT_VAR1: 'some key'
  ENVIRONMENT_VAR2: 'some key'
  ENVIRONMENT_VAR3: 'some key'

我正在使用 os.Getenv("ENVIRONMENT_VAR1") 来检索 key ，当我在本地运行它时它可以工作，但在部署到谷歌应用引擎时无法工作。

Answer 1

它在官方文档中没有记录:Defining environment variables ，但是在 app.yaml 中定义的环境变量在生产中不会在调用 init() 函数之前设置。它们仅在服务第一个请求之前设置。

已报告此问题 here .引用 AppEngine 工程师的回答:

Right. Due to the nature of the implementation, environment variables are not available in your init functions, unfortunately. Although they are not tied to requests, they are not set until after all the init functions have already run, but are set before the first request is handled.

As a result, you could use a sync.DoOnce in your main handler to perform any actions required based on the value of an environment variable since it will be properly set by that time.

使用 Once.Do() 实现此目的的示例:

var once = sync.Once{}

func MainHandler(w http.ResponseWriter, r *http.Request) {
    once.Do(mysetup)
    // do your regular stuff here
}

func mysetup() {
    // This function is executed only once. Read / use env vars here.
    var1 := os.Getenv("ENVIRONMENT_VAR1")
    _ = var1 // use var1
}