解析时间时，Mac OSX上的Golang空位置

Question

(Edit/update): Thanks to @djd for pointing out that we can skip all the JSON/struct decoding business; the key issue is with time.Parse.

The same issue comes up here where the Location is "empty" rather than UTC (I would've expected UTC based on the docs: https://golang.org/pkg/time/#Parse

"In the absence of a time zone indicator, Parse returns a time in UTC."

Here's the example code: https://play.golang.org/p/pb3eMbjSmv

package main

import (
    "fmt"
    "time"
)

func main() {
    // Ignoring the err just for this example's sake!
    parsed, _ := time.Parse(time.RFC3339, "2017-08-15T22:30:00+00:00")
    fmt.Printf("String(): %v
", parsed.String())
    fmt.Printf("Location(): %v
", parsed.Location())
}

which outputs

String(): 2017-08-15 22:30:00 +0000 +0000
Location():

So while the offset of the time.Time's Location appears to be correct, its timezone name is just an empty string. Running in on other machines (and The Go Playground) give the expected "UTC" location.

[Original post]:

When decoding a timestamp field from JSON into a struct on my local OS X machine, the Location of the time.Time field is "empty" rather than UTC. This is problematic for me running unit tests locally (vs. on a CI server where the Location is being set correctly to be UTC).

When I run that on my machine, I see

go run main.go TimeField.String(): 2017-08-15 22:30:00 +0000 +0000 TimeField.Location():

So while the offset of the time.Time's Location appears to be correct, its timezone name is just an empty string. This is using Go 1.5:

go version go version go1.5 darwin/amd64

Answer 1

I find same behavior using my current setup on Mac and I suspect it will be same behavior on Linux (not sure through)

$ go version
go version devel +31ad583 Wed Aug 10 19:44:08 2016 +0000 darwin/amd64

To make it more deterministic, I suggest using a custom json Unmarshal like so:

package main

import (
  "encoding/json"
  "fmt"
  "strings"
  "time"
)

type Time struct {
   *time.Time
}

func (t *Time) UnmarshalJSON(b []byte) error {
  const format = "\"2006-01-02T15:04:05+00:00\""
  t_, err := time.Parse(format, string(b))
  if err != nil {
      return err
  }
  *t = Time{&t_}
  return nil
}

type Example struct {
  TimeField *Time `json:"time_field"`
}

func main() {
  inString := "{\"time_field\": \"2017-08-15T22:30:00+00:00\"}"
  var ex Example
  decoder := json.NewDecoder(strings.NewReader(inString))
  decoder.Decode(&ex)
  fmt.Printf("TimeField.String(): %v
", ex.TimeField.String())
  fmt.Printf("TimeField.Location(): %v
", ex.TimeField.Location())
}