Golang Global Variable access

Question

I'm fairly new to golang, this should be a simple answer but I've tried searching every where with no luck.

How do I access a global variable that was declared/init in my main.go in a different .go package/file? Keeps telling me that the variable is undefined (I know that global variables are bad but this is just to be used as a timestamp)

in main.go

var StartTime = time.Now()
func main(){...}

trying to access StartTime in a different .go file but keep getting StartTime undefined

Possible duplicate of go build works fine but go run fails – Ainar-G Jan 27 '16 at 13:42 — Ainar-G, Jan 27 '16 at 13:42
Is the first letter on the variable name capitalized? – olif Jan 27 '16 at 13:43 — olif, Jan 27 '16 at 13:43
Yes, it is capitalized, and my go build fails – Nighthee Jan 27 '16 at 13:44 — Nighthee, Jan 27 '16 at 13:44
are you including all relevant files when running the program? That is, when running the code, are you running go run file1.go file2.go ..etc – olif Jan 27 '16 at 13:45 — olif, Jan 27 '16 at 13:45
Yes, to be more concise, I have a variable called 'var StartTime = time.Now()' in my main.go But when i try to access StartTime in a different .go of the same directory, it says its undefined, would i have to include "main" in the .go file that im trying to call? – Nighthee Jan 27 '16 at 13:47 — Nighthee, Jan 27 '16 at 13:47

olif · Accepted Answer · 2016-01-27 14:19:24Z

I would "inject" the starttime variable instead, otherwise you have a circular dependency between the packages.

main.go

var StartTime = time.Now()
func main() {
   otherPackage.StartTime = StartTime
}

otherpackage.go

var StartTime time.Time

Hi I'm Frogatto · Answer 2 · 2017-11-26 05:40:10Z

I create a file dif.go that contains your code:

package dif

import (
    "time"
)

var StartTime = time.Now()

Outside the folder I create my main.go, it is ok!

package main

import (
    dif "./dif"
    "fmt"
)

func main() {
    fmt.Println(dif.StartTime)
}

Outputs:

2016-01-27 21:56:47.729019925 +0800 CST

Files directory structure:

folder
  main.go
  dif
    dif.go

It works!

My 'dif' is a restful API and won't be called when the program starts but only when its invoked through URL, so i need to put the StartTime in main.go and pass it to dif, you're passing it from dif to main, thanks for the try though! – Nighthee Jan 27 '16 at 14:05 — Nighthee, Jan 27 '16 at 14:05

Golang Global Variable access

2 Answers