x/crypto/acme: not possible to remove contact information

[mateusz834]

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

$ go version
go version go1.18.2 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="/home/mateusz/go/bin"
GOCACHE="/home/mateusz/.cache/go-build"
GOENV="/home/mateusz/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/mateusz/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/mateusz/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.2"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
GOWORK=""
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-build947326088=/tmp/go-build -gno-record-gcc-switches"

What did you do?

c := &acme.Client{
    DirectoryURL: "https://acme-staging-v02.api.letsencrypt.org/directory",
    Key:          key,
}
c.UpdateReg(ctx, &acme.Account{
    Contact: nil,
})

What did you expect to see?

Contact information removed

What did you see instead?

Contact information didn't change

c := &acme.Client{
    DirectoryURL: "https://acme-staging-v02.api.letsencrypt.org/directory",
    Key:          key,
}
acct, _ := c.GetReg(ctx, "")
fmt.Println(acct.Contact) // ["mailto:email@gmail.com"]

[mateusz834]

It is caused by the "omitempty": https://github.com/golang/crypto/blob/6f7dac9698988af7b704298c9fd8adf58e1d30c0/acme/rfc8555.go#L109