cmd/go: go build doesn't build module if name is used by standard library and stops without warning/error.

[Omkar76]

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

$ go version
go version go1.15.3 linux/amd64

Does this issue reproduce with the latest release?

yes, with go1.15.3

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/onkar/.cache/go-build"
GOENV="/home/onkar/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/onkar/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/onkar/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/mnt/data/go/logging/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-build208606108=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I created a new go.mod file by running go mod init log. here log is module name.
then after writing some code in main package, I tried to build by executing go build at root of my module.
That did nothing. No binary was built. After searching on internet for a while I found that module names without a dot in first component are reserved for standard library.

What did you expect to see?

I expected a warning message saying that 'log' is name of a standard library module and should not be used
Or
warning message like - module names should contain dot in first component.

What did you see instead?

The go build stopped without building module with no error / warnings.

[bcmills]

Duplicate of #39285