missing dot in first path element when building from official golang Docker image

[lucas-dehandschutter]

What version of Go are you using (go version)?

$ go version
go version go1.13.8 linux/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY="git.my.company.com"
GONOSUMDB="git.my.company.com"
GOOS="linux"
GOPATH="/go"
GOPRIVATE="git.my.company.com"
GOPROXY="https://repo.my.company.com/artifactory/api/go/proxy-go"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/go/myapp/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build900476856=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I have a Go module project organized as follow:

/myapp
└── /src
    └── /foo 
        └── bar.go
└── main.go 
└── go.mod           
└── Dockerfile

The main.go file looks like this:

package main

import "myapp/src/foo"

func main() {
	foo.bar()
}

go.mod:

module myapp

go 1.13

require git.my.company.com/golang/anotherdep v1.0.3

On my workstation, this project build correctly with go build main.go

Now, I want to build this project from a Dockerfile in order to integrate it in a deployment pipeline.

The Dockerfile is as follow:

FROM golang:1.13.8-buster as build
ENV GO111MODULE="on"
ENV GOPROXY="https://repo.my.company.com/artifactory/api/go/proxy-go"
ENV GOPRIVATE="git.my.company.com"

RUN mkdir myapp
COPY ./* ./myapp/
WORKDIR ./myapp/
RUN go env
RUN go build -o app -v -x main.go

When I build this project from the Dockerfile, it fails:

$ docker build --no-cache -t myapp .
...
build command-line-arguments: cannot load myapp/src/foo: malformed module path "myapp/src/foo": missing dot in first path element

go env Output from my workstation

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/me/.cache/go-build"
GOENV="/home/me/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY="git.my.company.com
GONOSUMDB="git.my.company.com"
GOOS="linux"
GOPATH="/home/me/go"
GOPRIVATE="git.my.company.com"
GOPROXY="https://repo.my.company.com/artifactory/api/go/proxy-go"
GOROOT="/snap/go/5364"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/snap/go/5364/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/me/gitrepo/myapp/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build720872982=/tmp/go-build -gno-record-gcc-switches"

go env Output from the build container

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOENV="/root/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY="git.my.company.com"
GONOSUMDB="git.my.company.com"
GOOS="linux"
GOPATH="/go"
GOPRIVATE="git.my.company.com"
GOPROXY="https://repo.my.company.com/artifactory/api/go/proxy-go"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/go/myapp/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build900476856=/tmp/go-build -gno-record-gcc-switches"

[bcmills]

The error message is not wrong.

Since there is no go.mod file in your project, main.go is not within a module, and the location of package myapp/src/foo is not specified.

The error message should at least be more helpful in Go 1.14. (See #32027.)

[bcmills]

For more information on how to set up a project using Go modules, see the series of blog posts starting with https://blog.golang.org/using-go-modules.

[lucas-dehandschutter]

There is a go.mod in my project

Here is the file

module myapp

go 1.13

require git.my.company.com/golang/anotherdep v1.0.3

[lucas-dehandschutter]

I just find out that the issue came from the copy instruction in my Dockerfile.
I used

COPY ./* ./myapp/

instead of

COPY . ./myapp/