time: location data always falls back to UTC in js/wasm

[eternal-flame-AD]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.11.1 linux/amd64

Does this issue reproduce with the latest release?

Yes.

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/ef/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/ef/code/go/"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/go"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build929309457=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Build and run the following snippet both in linux/amd64(local architecture) and wasm/js

package main

import (
	"fmt"
	"time"
)

func main() {
	fmt.Println(time.Now().Location())
}

What did you expect to see?

The results should be consisitent with the following javascript code, which should return the OS timezone info:

console.log(Intl.DateTimeFormat().resolvedOptions().timeZone)

What did you see instead?

On native architecture(linux/amd64):

Asia/Shanghai

On browser javascript:

Asia/Shanghai

On wasm:

UTC

[agnivade]

zoneinfo_unix.go seems to contain js,wasm. Hence in a browser environment, it falls back to UTC. I think it should be possible to have a zoneinfo_js.go and call into wasm_exec.js to get the browser/node timezone.

[eternal-flame-AD]

Yep, I think it require at least a bit of refactoring on the time package as the current infrastructure of the time package is not designed to handle handle timezone operations using syscall

[gopherbot]

Change https://golang.org/cl/143577 mentions this issue: time: return correct zone info for wasm