running go install with golang exec.Command

Question

I'm trying to write some code for a webhook, that will call go install. The problem i'm having is that the GOPATH isn't set when i call any go commands with exec.Command

func exec_cmd(w http.ResponseWriter, cmd string, args ...string) {
    command := exec.Command(cmd, args...)
    var out bytes.Buffer
    var stderr bytes.Buffer
    command.Stdout = &out
    command.Stderr = &stderr
    err := command.Run()
    if err != nil {
        errstring := fmt.Sprintf(fmt.Sprint(err) + ": " + stderr.String())
        io.WriteString(w, errstring)
    }
    io.WriteString(w, out.String())
    fmt.Println(out.String())
}

func webhook(w http.ResponseWriter, r *http.Request) {
    exec_cmd(w, "go", "install", "github.com/me/myrepo/mything")
}

func test(w http.ResponseWriter, r *http.Request) {
    io.WriteString(w, "test")
}

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/webhook", webhook)
    mux.HandleFunc("/", test)
    http.ListenAndServe(":8000", mux)
}

when the webhook endpoint is hit, it gives:

exit status 1: can't load package: package github.com/me/myrepo/mything: cannot find package "github.com/me/myrepo/mything" in any of:
    /usr/lib/go-1.6/src/github.com/me/myrepo/mything (from $GOROOT)
    ($GOPATH not set)

How would i go about making sure the GOPATH is set in this context?

If i run "go install github.com/me/myrepo/mything" from the command line, it works fine.

You should also update your version of Go, if only because go1.8 introduced a default GOPATH. — Mr_Pink
– Mr_Pink, Commented Mar 21, 2017 at 22:28

Kenny Grant · Accepted Answer · 2017-03-21 21:38:09Z

2

Are you running this in your editor context, or in a container perhaps? It won't work in a context without the GOPATH env variable set.

If running with go run main.go, does it work? It works for me in that context without modifying your code. As long as the parent context has access to GOPATH it should. You could alternatively set it manually with something like this:

command.Env = append(os.Environ(), "GOPATH=/tmp/go")

Or you could set GOPATH (for install) and PATH (for go,git cmds) in the context this process will run in (probably preferable), for example in a systemd unit file.

answered Mar 21, 2017 at 21:38

Kenny Grant

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1 Comment

usrgnxc Over a year ago

setting the Env is working perfectly now, thanks. Setting it in systemd process file is probably better though, i didn't realise i could do that.

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