x/playground: upgrade to 1.12

[iporsut]

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

$ go version
go version go1.12 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/weerasak/go/bin"
GOCACHE="/Users/weerasak/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/weerasak/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
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/9k/pvfwqqzn6fqbpwghhrcjkm480000gn/T/go-build282905208=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I run godoc -play that distributed with go 1.12 then open http://localhost:6060/pkg/strings/#ReplaceAll and run example.

What did you expect to see?

moo moo moo

What did you see instead?

prog.go:9:14: undefined: strings.ReplaceAll

[iporsut]

The root cause because godoc sending example code to compile at https://play.golang.org/compile that still use v1.11.1.

[agnivade]

/cc @dmitshur

[dmitshur]

Indeed, the playground is still on Go 1.11.1, as https://play.golang.org/p/Ztyu2FJaajl reports.

I'll redeploy it with Go 1.12 now.

[iporsut]

I'v checked https://play.golang.org/p/Ztyu2FJaajl it 1.12 now thanks.

[gopherbot]

Change https://golang.org/cl/163798 mentions this issue: playground: use Go 1.12