如何在数组中写入 map 并将其添加到 go 中的 json 文件中？

Question

I want to make a sign-up server using go where the users are stored in a JSON file called users.json with this format:

[
    {
        "email": "email",
        "password": "password"
    },
    {
        "email": "email",
        "password": "password"
    },
    ...
]

Right now I'm using this code:

func signup(w http.ResponseWriter, r *http.Request) {
    r.ParseForm()

    type User struct {
        Email    string
        Password string
    }

    user := User{}
    user.Email = r.Form["email"][0]
    user.Password = r.Form["password"][0]

    content, err := json.Marshal(user)
    if err != nil {
        fmt.Println(err)
    }
    err = ioutil.WriteFile("users.json", content, 0644)
    if err != nil {
        log.Fatal(err)
    }
}

The issue with it is that if a new user signed up it deletes the old data in the JSON file and it stores the informations in this format:

{
    "Email": "email",
    "Password": "password"
}

I'm new to go and have no idea on how to do it.

Answer 1

Doc says: WriteFile writes data to the named file, creating it if necessary. If the file does not exist, WriteFile creates it with permissions perm (before umask); otherwise WriteFile truncates it before writing, without changing permissions.

https://pkg.go.dev/os#WriteFile

You must append to the JSON file. Follow this thread to see how you can perform JSON file append. https://stackoverflow.com/a/44642209/9787555