Golang中的编组/解组时间对象意外失败

Question

Unmarshalling a marshalled time object is failing, because of a few characters

Test

declare the following:

// values
now := time.Now()
timeToJSON, _ := json.Marshal(now)
var obj time.Time
json.Unmarshal(timeToJSON, &obj)

then do the following test logic:

if !assert.Equal(t,
    now.String(),
    obj.String()) {
    t.FailNow()
}

Expected

the test to pass, and the two objects to be equal

Actual

It fails:

--- FAIL: TestFromJSON (0.00s)
    D:\dev2017\GO\src\ezsoft\apiserver_sdk\model\delete\deleteModel_test.go:94: 
            Error Trace:    deleteModel_test.go:94
            Error:          Not equal: 
                            expected: "2018-09-04 10:36:18.3627338 -0400 EDT m=+0.014000801"
                            actual  : "2018-09-04 10:36:18.3627338 -0400 EDT"

                            Diff:
                            --- Expected
                            +++ Actual
                            @@ -1 +1 @@
                            -2018-09-04 10:36:18.3627338 -0400 EDT m=+0.014000801
                            [phone]:36:18.3627338 -0400 EDT
            Test:           TestFromJSON
FAIL
FAIL    ezsoft/apiserver_sdk/model/delete   1.336s
Error: Tests failed.

NOTE

I notice that, upon inspecting the output, that, somehow, some m=+[blah] is being appended to expected/actual.

I don't know why, however, and skimming RFC 3339 doesn't give me any hints why.

Answer 1

Per the documentation, the m value is the monotonic clock value, which can be removed using Truncate for comparisons not for the purpose of timing. The m field does not match because it is omitted from JSON, it is only generated by time.Now().

Try like so:

// values
now := time.Now().Truncate(0)  // Truncate to remove monotonic clock portion
timeToJSON, _ := json.Marshal(now)
var obj time.Time
json.Unmarshal(timeToJSON, &obj)

The monotonic clock offset was added in order to allow for accurate timing of durations which span a wall clock change (e.g. NTP update, DST change, or leap second/smear).