CODEWITHSUNDEEP
govgo
CommonSenseCode
CommonSenseCode

Reputation: 25418

Golang: How to use vgo? error: "cannot find package"

  1. I have a project which is currently under my GOPATH /usr/local/go/src/

  2. Then I went inside my project root and ran: go get -u golang.org/x/vgo

  3. In my main.go I want to use lib httprouter so I added in import statement:

    import ( "github.com/julienschmidt/httprouter" )

  4. I ran vgo build

  5. Then when I start to run my server as usual I get the following error:

main.go:8:2: cannot find package "github.com/julienschmidt/httprouter" in any of: /usr/local/go/src/github.com/julienschmidt/httprouter (from $GOROOT) /Users/myuser/go/src/github.com/julienschmidt/httprouter (from $GOPATH)

I understand the error, it seems to be searching for httprouter under GOPATH or GOROOT. So do I have to do anything else to just let vgo do its thing and I can run my server successfully?

Upvotes: 2

Views: 5730

Answers (1)

Tyler B
Tyler B

Reputation: 1698

Using vgo build

Here is a "Hello, World" walk-through of using vgo, including common errors and how to respond to them.

  1. $ go get -u golang.org/x/vgo
  2. $ cd /tmp/hello # Outside of GOPATH.

  3. $ cat main.go

    package main

import "fmt"

func main() {
    fmt.Println("Hello, World")
}

  4. $ vgo build

    cannot determine module root; please create a go.mod file there

  5. This error tells us we need to specify what the root of our vgo module is. A module is a collection of packages (possibly one) versioned together. Create an empty go.mod file to signify this is the module root:

    $ touch go.mod

  6. Try building again: $ vgo build.

    vgo: cannot determine module path for source directory
/tmp/hello (outside GOPATH, no import comments)

  7. This error tells us vgo doesn't know the import path of our package. There are two ways to tell it:

    1. Add a module statement to go.mod.
    2. Add an import comment to our package.

    We'll go with option 2 right now and come back to option 1. Change the first line of main.go to be:

    package main // import "my/import/path/hello"

  8. $ vgo build one last time.

  9. Run the binary: $ ./hello

    Hello, World

Note: go.mod now contains a module line (option 1 above):

$ cat go.mod 
module my/import/path/hello

If you are inside your GOPATH, the error in step 5 should not occur - vgo build should automatically figure out you're inside your GOPATH and add the module line accordingly.

Using vgo run (without using vgo build)

For this example, lets use the hello.go from the A Tour of Versioned Go (vgo):

  1. $ go get -u golang.org/x/vgo
  2. $ mkdir /tmp/hello2
  3. $ curl -sS https://swtch.com/hello.go >hello.go

  4. $ vgo run hello.go

    cannot determine module root; please create a go.mod file there

  5. $ touch go.mod

  6. $ vgo run hello.go

    vgo: resolving import "rsc.io/quote"
vgo: finding rsc.io/quote (latest)
vgo: adding rsc.io/quote v1.5.2
Hello, world.

Upvotes: 4

Related Questions