全局变量不能从CLI命令中保留

Question

package main

import (
    "fmt"
    "net/http"
    "os"
    "strconv"

    "github.com/go-chi/chi"
)

var tests []string

func main() {

    if len(os.Args[:]) > 1 {
        tests = append(tests, "test")
        fmt.Println(strconv.Itoa(len(tests)) + " tests")
        os.Exit(0)
    }

    r := chi.NewRouter()
    r.Get("/", func(w http.ResponseWriter, r *http.Request) {
        tests = append(tests, "test")
        fmt.Println(strconv.Itoa(len(tests)) + " tests")
    })

    http.ListenAndServe(":8086", r)
}

When i access the program from localhost:8086 it works okay and i can see len(tests) increment when i refresh.

But when i access the program with ./test arg command, len(tests) increments to 1 but then gets lost, so next time it says 1 and never goes any higher.

I thought that these two methods should also share the same tests value, but when i write to one, the other can't read it etc.

Thanks.

Answer 1

tests is a global variable. As long as your process is running, it will keep its value.

However, when you run ./test arg, this starts a new process, adds an element to tests, then exits. The next invocation of ./test arg is a completely new process, it has no way of sharing information with the previous invocation.

The process running with ./test arg is also completely different from the currently-running web server started with ./test. Same thing: they share no state, they just happen to be the same binary.

If you want to persist something between invocations of a given program, you need to save the data somewhere (file, database, etc...).