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

go version go1.15 darwin/amd64

Does this issue reproduce with the latest release?

This is proposal. So, yes.

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

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users//Library/Caches/go-build"
GOENV="/Users//Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users//go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users//go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.15/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.15/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/nx/_fxcwls90392z82dwl07768r0000gn/T/go-build100053484=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

1. make a go module
   go.mod

module gitlab.my-work.int/some-long-path/some-project-name/some-project-part

go 1.15

2. add go files to module. Add internal imports to each other. Use some short notation for internal references.
   ./tools/plus.go

package tools
func Plus(a,b int) int { return a+b }

./one.go

package main

// import gitlab.my-work.int/some-long-path/some-project-name/some-project-part/tools. // currently working scenario
import LOCAL/tools. // works according this proposal. "LOCAL" - is an example label for current module
  
func main(){
   fmt.Println(tools.Plus(1,2))
}

What did you expect to see?

LOCAL imports works.

What did you see instead?

LOCAL/tools not found.
go build/get even try to download it.

Some motivation details

Clones

Can't make go-gettable fork of golang module without changing every file in it.
In order to make fork to be a valid module you should change it's module name according repo name. And all imports in all files as consequence.
Of course, there will be troubles in sync process later.

IDE

Currently on any typo in internal imports, "go get" will try to download internal package. And error will not be "hey, there is typo in your import", but "some server returned 404" or even "invalid credentials" for non-public repos.

Import ordering

Clear way to order internal imports into separate block. Currently its a complex task for code analyze systems.

Just shorter and more clear

Yes, just shorter and more clear