datastore: civil package types are loaded incorrectly when local machine timezone is not UTC

[dnerdy]

Client

Datastore

Environment

Any

Go Environment

$ go version
go version go1.14.12 darwin/amd64
$ go env
[I believe this is unrelated.]

Code

The pre-existing TestLoadToInterface test fails when run on a machine that has a timezone set to a non UTC timezone.

cd datastore
go test ./... -run TestLoadToInterface

Also, the TestLoadToInterface/struct_with_civil.Date would fail when run on a machine set to Pacific time if the test timestamp was 1605504600 (11/16/2020 @ 5:30am UTC) instead of 1605474000 (11/15/2020 @ 9:00pm UTC).

Expected behavior

I would expect the above tests to pass when run on a machine with any non-UTC timezone.

Actual behavior

--- FAIL: TestLoadToInterface (0.00s)
    --- FAIL: TestLoadToInterface/struct_with_civil.DateTime (0.00s)
        load_test.go:565: Mismatch: got - want +
              &struct{ DateTime civil.DateTime }{
              	DateTime: civil.DateTime{
              		Date: civil.Date{
              			Year:  2020,
              			Month: s"November",
            - 			Day:   15,
            + 			Day:   16,
              		},
              		Time: civil.Time{
            - 			Hour:       21,
            + 			Hour:       5,
              			Minute:     30,
              			Second:     0,
              			Nanosecond: 0,
              		},
              	},
              }
    --- FAIL: TestLoadToInterface/struct_with_civil.Time (0.00s)
        load_test.go:565: Mismatch: got - want +
              &struct{ Time civil.Time }{
              	Time: civil.Time{
            - 		Hour:       21,
            + 		Hour:       5,
              		Minute:     30,
              		Second:     0,
              		Nanosecond: 0,
              	},
              }
FAIL
FAIL	cloud.google.com/go/datastore	0.869s
ok  	cloud.google.com/go/datastore/admin/apiv1	0.559s [no tests to run]
?   	cloud.google.com/go/datastore/internal/gaepb	[no test files]
FAIL

(Also note the comment above about how TestLoadToInterface/struct_with_civil.Date also fails under some circumstances).

Additional context

I left a common on #3202 with information about how the loading can be corrected.

cc @codyoss

[codyoss]

Thanks!

[tritone]

@dnerdy let me know if this fix did the trick for you!

[dnerdy]

Looks good 👍