cmd/go: replace directive causes build to take 30 seconds

[levblanc]

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

$ go version
go version go1.11.4 darwin/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
GOARCH="amd64"
GOBIN="/Users/levblanc/go/bin"
GOCACHE="/Users/levblanc/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/levblanc/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/levblanc/projects/x-crypto-issue/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/yk/p1tyzt2n5m38k09cbsgktxhh0000gn/T/go-build141072027=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

• imported golang.org/x/crypto/bcrypt in my program

• alias golang.org/x/[email protected] to github.com/golang/crypto@latest with go mod

Here is the repo to reproduce the problem.

You can find detailed description and my thoughts in the README file.

What did you expect to see?

go run main.go works as normal.

What did you see instead?

go run main.go takes around 30 seconds to print out the result of my simple program,

while go run -mod=vendor main.go works well.

[bcmills]

Duplicate of #27859.