go.mod versions seem to require tags beginning with "v" to properly resolve.

[theherk]

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

$ go version
go version go1.13 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="/home/h4s/.cache/go-build"
GOENV="/home/h4s/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/h4s/projects/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"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/h4s/projects/cleardata.com/aws/raws/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-build119312209=/tmp/go-build -gno-record-gcc-switches"
GOROOT/bin/go version: go version go1.13 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.13
uname -sr: Linux 5.3.1-arch1-1-ARCH
/usr/lib/libc.so.6: GNU C Library (GNU libc) stable release version 2.29.

What did you do?

• push tag 0.1.0 to the same ref as master
• go get -u -v github.com/cleardataeng/aidews
• go.mod shows psuedo version
• manually update go.mod to 0.1.0
• go get -u -v github.com/cleardataeng/aidews
• go.mod shows psuedo version
• push tag v0.1.0 to the same hash
• go get -u -v github.com/cleardataeng/aidews
• go.mod reflects correct version

What did you expect to see?

I expected any tag that resolves to the tip of the default branch to be used as the version identifier.

What did you see instead?

That only tags beginning with "v" were treated accordingly.

Maybe this is not a bug, but I can't see why any tag resolving to the current head wouldn't be treated as the version identifier. Semver 2 is much less explicit about tagging, but the "v" is explicitly not part of the version. So are we after tags or version numbers? If version numbers, the "v" should go. If tags, I'd think any tags regardless of version sufficient.

[seankhliao]

please see #30146

[bcmills]

Duplicate of #32945