英文:
How to build a program with a foreign main function?
问题
我正在写一个框架，并且希望将 HTTP 服务器的初始化部分作为该框架的一部分。基本上，我有一个名为 "internal" 的包，如下所示，该包被框架中间件导入：
package internal
import (
"net/http"
"log"
)
func main() {
checkHealth(http.DefaultServeMux)
if err := http.ListenAndServe(":8080", http.HandlerFunc(handleHTTP)); err != nil {
log.Fatalf("http.ListenAndServe: %v", err)
}
}
在应用程序代码中，我希望在 init 函数中定义处理程序，例如：
func init() {
http.HandleFunc("/", handler)
}
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprint(w, "Hello, world!")
}
然而，如果我在应用程序代码目录/包中运行 "go build"，它会报错说未定义 main 函数：
runtime.main_main: main.main: not defined
runtime.main_main: undefined: main.main
所以我的问题是，我应该如何构建/编译程序，为什么使用标准的 "go build" 命令找不到在 internal 包中定义的 main 函数。
英文:
I'm writing a kind of framework and I would like to make the initialisation of the http server part of this framework. So basically I have a package internal as below which is imported by the framework middleware:
package internal
import(
"net/http"
"log"
)
func main() {
checkHealth(http.DefaultServeMux)
if err := http.ListenAndServe(":8080", http.HandlerFunc(handleHTTP)); err != nil {
log.Fatalf("http.ListenAndServe: %v", err)
}
}
In the app code I'm looking to define the handlers in an init function.
e.g.
func init() {
http.HandleFunc("/", handler)
}
func handler(w http.ResponseWriter, r *http.Request) {
fmt.Fprint(w, "Hello, world!")
}
However if I run go build in the app code directory/package it errors out that the main function is not defined:
runtime.main_main: main.main: not defined
runtime.main_main: undefined: main.main
So my question is how should I build / compile the program so and why using the standard go build command it doesn't find the main function defined in the internal package.
答案1
得分: 4
main 函数必须在 main 包中：程序执行
程序的执行从初始化
main包开始，然后调用main函数。当该函数调用返回时，程序退出。它不会等待其他（非主）goroutine 完成。
如果你想要在启动时初始化某些状态，或者通过简单地导入一个包来产生副作用，你可以使用一个 init 函数。然而，init 函数必须返回，所以你不能在其中使用 http.ListenAndServe 阻塞。
英文:
The main function must be in the main package: Program Execution
> Program execution begins by initializing the main package and then invoking the function main. When that function invocation returns, the program exits. It does not wait for other (non-main) goroutines to complete.
If you want a package to initialize some state at start up, or have side-effects by simply importing it, you use an init function. The init however must return, so you can't block with it http.ListenAndServe.
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