CODEWITHSUNDEEP
visual-studiogovs-community-edition
Sooraj
Sooraj

Reputation: 524

Cannot run multiple go files

I have two go files in a directory. 

  Go  
   ├── mains.go  
   └── vars.go

The code for the mains.go and vars.go are given below:

mains.go
--------
package main

import "fmt"

func main() {
     fmt.Println("This is the mains file")
}


vars.go
--------
package main

import "fmt"

func main() {
     fmt.Println("This is the vars file")
}

While running the file individually using the terminal command

go run mains.go
go run vars.go

I am getting the output. When I am using VScode, I am getting the following error

main redeclared in this block
previous declaration at ./mains.go:5:6

Due to this error, I am not able to run the code. The code runs fine when each file is separated into folders. I tried to remove the main declaration from the file before saving but the autocomplete/autoformat feature fills the package main & import "fmt" commands automatically. My doubts are :

My specs

Ubuntu : 16.04
Visual Studio Code : 1.23.1
go version : 1.9.2

Upvotes: 4

Views: 2334

Answers (3)

Vladimir Mur
Vladimir Mur

Reputation: 1

Mulitple go files with func main() in the same folder is convinient for simple code snippents (not production code!).

You cannot use go build on that folder. Go will give an error:

main redeclared in this block

But you can run individual files using command

go run file.go

To run single file in VSCode you have to add Launch file configuration to VSCode

  1. Press Gear next to Run triangle button Open 'launch.json'
  2. In the lower right part of the screen appears button Add configuration. Press it.
  3. Select '{} Go: Launch file' option from the list.

Added new configuration would be:

        {
            "name": "Launch file",
            "type": "go",
            "request": "launch",
            "mode": "debug",
            "program": "${file}"
        },
  1. Save launch.go
  2. To run your file select 'Launch file' in the drop down list next to Run triangle button.

Upvotes: 0

smartmek
smartmek

Reputation: 51

It doesn't make sense to redeclare the main function twice in the same package. You mentioned that the code works fine placing the mains.go and vars.go files in separate folders. That is expected and this is what needs to be done - placing the files in different folders.

If however, you need to run both functions, change your setup using a simple goroutine as defined below:

// main.go
package main

import (
          "fmt"
          "sync"
)

var wg sync.WaitGroup

func main() {
     fmt.Println("This is the mains file")

     wg.Add(1)
     go vars()

     // do other stuff...
     wg.Wait()
}

// vars.go
package main

import "fmt"

func vars() {
     fmt.Println("This is the vars file")
     // do other stuff...

     wg.Done()
}

This would allow you to run both functions at the same time whilst still in the same package. Since the functions can't have the same function name: main(), you need to change one of them to something else as I've done.

Note however that you could simply call the vars() function without doing so concurrently.

Upvotes: 2

kashpatel
kashpatel

Reputation: 725

Have you declared two main functions in two different files in same directory? If yes, you can not as you can only have single entry point for go program.

Also Golang recommends to have single package per directory. You can have multiple file in a same package.

For example:

- Root directory of program
   -- main.go - package main (define main func here) 
   -- vars.go - package main (You can not redefine main func or package in this file, since everything under directory falls in to same package in golang)

   - lib directory
   -- lib.go - package lib
   -- something.go - package lib

Hope that helps!

Upvotes: 1

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