Go error: go : go.mod file not found in current directory or any parent directory; (working on GOPATH/src)

Question

I installed Golang and faced with go.mod file not found in current directory or any parent directory error at very first time.

But I'm working on <GOPATH>/src directory. Isn't go.mod only required if current working directory is located out of GOPATH?

Here's detailed information

Go version : go version go1.16.4 windows/amd64

Go env :

set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\<userName>\AppData\Local\go-build
set GOENV=C:\Users\<userName>\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\<userName>\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\<userName>\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.16.4
set GCCGO=gccgo
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=NUL
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\<userName>\AppData\Local\Temp\go-build4258913208=/tmp/go-build -gno-record-gcc-switches

Working directory: C:\Users\<userName>\go\src\main.go

Code :

package main

import "fmt"

func main() {
    fmt.Println("HELLO")
}

And Error:

go: go.mod file not found in current directory or any parent directory; see 'go help modules'
Build process exiting with code: 1 signal: null

p.s. I'm using VS Code

Answer 1

"The go command now builds packages in module-aware mode by default, even when no go.mod is present."

"You can set GO111MODULE to auto to enable module-aware mode only when a go.mod file is present in the current directory or any parent directory."

At your command prompt

go env -w GO111MODULE=auto

New module changes in Go 1.16

Answer 2

Learning golang as well and I ran into this issue as well.

This solved it for me:

go mod init

That will create a base go.mod file with the module and version information to run go install if working out of the $GOPATH workspace. I do agree learning more about the Go module system and not turning off the env var, but to get up and running this seemed fine.

Answer 3

As of Go 1.16, the GO111MODULE environment variable is treated as "on" by default, meaning Go expects to find a go.mod file, and no longer falls back to pre-module GOPATH behavior.

If you want to go back to the pre-1.16 behavior, you now have to explicitly specify GO111MODULE=auto, but you're far better off creating a go.mod file.

See https://golang.org/doc/go1.16#go-command and https://golang.org/ref/mod

Answer 4

Create a go.mod file, examples:

go mod init example.com/m    # to initialize a v0 or v1 module
go mod init example.com/m/v2 # to initialize a v2 module