Golang Global Variable access

golang 中全局变量的问题。

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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

variables
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edited Jan 27 ‘16 at 13:51 asked
Jan 27 ‘16 at 13:36

Nighthee
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2 Possible duplicate of go build works fine but go run fails – Ainar-G Jan 27 ‘16 at 13:42
Is the first letter on the variable name capitalized? – olif Jan 27 ‘16 at 13:43
Yes, it is capitalized, and my go build fails – 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
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

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2 Answers

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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

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edited Jan 27 ‘16 at 14:19 answered
Jan 27 ‘16 at 13:57

olif
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Yep it worked! Thanks! – Nighthee Jan 27 ‘16 at 14:34

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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!

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edited Nov 26 ‘17 at 5:40

Hi I‘m Frogatto
17.8k54887 answered
Jan 27 ‘16 at 14:02

joy miao
713

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