Non-declaration statement outside function body in Go

user_1575153 0
Viewed 86065

I'm building a Go library for an API that offers JSON or XML formatted data.

This API requires me to request a session_id every 15 minutes or so, and use that in calls. For example:

foo.com/api/[my-application-id]/getuserprofilejson/[username]/[session-id]
foo.com/api/[my-application-id]/getuserprofilexml/[username]/[session-id]

In my Go library, I'm trying to create a variable outside of the main() func and intend to ping it for a value for every API call. If that value is nil or empty, request a new session id and so on.

package apitest

import (
    "fmt"
)

test := "This is a test."

func main() {
    fmt.Println(test)
    test = "Another value"
    fmt.Println(test)

}

What is the idiomatic Go way to declare a globally-accessible variable, but not necesarilly a constant?

My test variable needs to:

  • Be accessible from anywhere within it's own package.
  • Be changeable
go global package scope variables
6 Answers

Short variable declarations i.e. :=, can ONLY be used within functions.

e.g.

func main() {
    test := "this is a test"
    // or
    age := 35
}

Declarations outside a function you must make use of keywords like var, func, const e.t.c depending on what you want (in this case we're using var).

Declaring a variable outside a function makes it accessible within its package.

package apitest

import (
    "fmt"
)
// note the value can be changed
var test string = "this is a test"

func main() {
    fmt.Println(test)
    test = "Another value"
    fmt.Println(test)

}

Extra info

If you want the variable to be accessible both within and outside its package, the variable has to be capitalized e.g.

var Test string = "this is a test"

this will make it accessible from any package.

user_45756450

We can declare variables as below:

package main

import (
       "fmt"
       "time"
)

var test = "testing"
var currtime = "15:04:05"
var date = "02/01/2006"

func main() {
    t := time.Now()
    date := t.Format("02/01/2006")
    currtime := t.Format("15:04:05")

    fmt.Println(test) //Output: testing
    fmt.Println(currtime)//Output: 16:44:53
    fmt.Println(date) // Output: 29/08/2018
}
user_54657900

Outside a function, every statement begins with a keyword (var, func, and so on) and so the := construct is not available.

You can read more information here: https://tour.golang.org/basics/10

user_63153660

I got this error when I was trying to run Go app with function definition like this:

(u *UserService) func GetAllUsers() (string, error) {...} //Error code

The correct way of defining a function (receiver function) was:

func (u *UserService) GetAllUsers() (string, error) {...} //Working code
user_101430180
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