bump golang version and use go.mod

2 jobs for v1.0.2-stable.3 in 14 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Test
failed #7229
run go checks

00:00:14

 
  Build
skipped #7230
build docker image
 
Name Stage Failure
failed
run go checks Test
	/usr/local/go/src/github.com/wcharczuk/go-chart/util (from $GOROOT)
/go/src/github.com/wcharczuk/go-chart/util (from $GOPATH)
build.go:25:3: cannot find package "golang.org/x/oauth2" in any of:
/usr/local/go/src/golang.org/x/oauth2 (from $GOROOT)
/go/src/golang.org/x/oauth2 (from $GOPATH)
global.go:23:3: cannot find package "golang.org/x/oauth2/github" in any of:
/usr/local/go/src/golang.org/x/oauth2/github (from $GOROOT)
/go/src/golang.org/x/oauth2/github (from $GOPATH)
ERROR: Job failed: exit code 1