http: superfluous response.WriteHeader

[fcddk]

my code:
http.Handle(*metricsPath, promhttp.Handler())

logs:
<30>2020-03-25T16:42:46.704128+08:00 cmp001 libvirt-qemu-exporter[21928]: 2020/03/25 16:42:46 http: superfluous response.WriteHeader call from libvirt-qemu-exporter/vendor/github.com/prometheus/client_golang/prometheus/promhttp.(*responseWriterDelegator).WriteHeader (delegator.go:58)
<30>2020-03-25T16:42:46.704923+08:00 cmp001 libvirt-qemu-exporter[21928]: 2020/03/25 16:42:46 http: superfluous response.WriteHeader call from exporter/vendor/github.com/prometheus/client_golang/prometheus/promhttp.(*responseWriterDelegator).WriteHeader (delegator.go:58)

[fcddk]

version v1.12.1

[beorn7]

v1.12.1

This repository currently only goes up to v1.5.1. Could you doublecheck which version you are using?

[fcddk]

I'm sorry, version: 1.2.1.

[beorn7]

Then this is probably a dupe of #672, fixed in v1.5.1. Please upgrade. If the problem still occurs, please follow up here, and I'll re-open.