Build of golang-github-ugorji-go fails due a panic in %check

...
Executing(%check): /bin/sh -e /var/tmp/rpm-tmp.5E3MO4
+ umask 022
+ cd /builddir/build/BUILD
+ cd go-ded73eae5db7e7a0ef6f55aace87a2873c5d2b74
+ export GOPATH=/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x//usr/share/gocode:/usr/share/gocode
+ GOPATH=/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x//usr/share/gocode:/usr/share/gocode
+ go test -compiler gc -ldflags '' github.com/ugorji/go/codec
--- FAIL: TestCborGoldens (0.00s)
--- FAIL: TestJsonCodecsTable (0.00s)
panic: [pos 17]: json: overflow integer after: 646464646 [recovered]
	panic: [pos 17]: json: overflow integer after: 646464646
goroutine 27 [running]:
testing.tRunner.func1(0xc42025e1a0)
	/usr/lib/golang/src/testing/testing.go:622 +0x338
panic(0x5afce0, 0xc420239ba0)
	/usr/lib/golang/src/runtime/panic.go:489 +0x32a
github.com/ugorji/go/codec.(*Decoder).errorf(0xc420259800, 0x677c24, 0x20, 0xc42003fa18, 0x1, 0x1)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/decode.go:1872 +0x202
github.com/ugorji/go/codec.(*jsonDecDriver).DecodeInt(0xc42000b500, 0x4000000000577ce0, 0xc420239b68)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/json.go:824 +0x3d6
github.com/ugorji/go/codec.(*Decoder).decode(0xc420259800, 0x577ce0, 0xc420239b68)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/decode.go:1581 +0x107c
github.com/ugorji/go/codec.(*Decoder).MustDecode(0xc420259800, 0x577ce0, 0xc420239b68)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/decode.go:1486 +0x3c
github.com/ugorji/go/codec.testCodecDecode(0xc42021f1c0, 0x11, 0x40, 0x577ce0, 0xc420239b68, 0x8c7460, 0x8faea0, 0x577ce0, 0xc420239b68)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/helper_test.go:166 +0x132
github.com/ugorji/go/codec.testUnmarshal(0x577ce0, 0xc420239b68, 0xc42021f1c0, 0x11, 0x40, 0x8c7460, 0x8faea0, 0xc42021f1c0, 0x11)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/codec_test.go:498 +0x5a
github.com/ugorji/go/codec.doTestCodecTableOne(0xc42025e1a0, 0x684660, 0x8c7460, 0x8faea0, 0xc420067c00, 0x1a, 0x38, 0xc4200bdb00, 0x1a, 0x21)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/codec_test.go:548 +0x44c
github.com/ugorji/go/codec.testCodecTableOne(0xc42025e1a0, 0x8c7460, 0x8faea0)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/codec_test.go:602 +0x19a
github.com/ugorji/go/codec.TestJsonCodecsTable(0xc42025e1a0)
	/builddir/build/BUILDROOT/golang-github-ugorji-go-0-0.10.gitded73ea.fc27.s390x/usr/share/gocode/src/github.com/ugorji/go/codec/codec_test.go:1396 +0x3c
testing.tRunner(0xc42025e1a0, 0x684550)
	/usr/lib/golang/src/testing/testing.go:657 +0xb6
created by testing.(*T).Run
	/usr/lib/golang/src/testing/testing.go:697 +0x32e
FAIL	github.com/ugorji/go/codec	0.013s
RPM build errors:
error: Bad exit status from /var/tmp/rpm-tmp.5E3MO4 (%check)
    Bad exit status from /var/tmp/rpm-tmp.5E3MO4 (%check)
Child return code was: 1
EXCEPTION: [Error()]
...

for full logs please see https://s390.koji.fedoraproject.org/koji/taskinfo?taskID=2528939


Version-Release number of selected component (if applicable):
golang-github-ugorji-go-0-0.10.gitded73ea.fc27

Additional info:
Same NVR builds OK in F-25 and F-24, so I suspect it's a golang 1.8 related issue.