#20 add prometheus metrics endpoint

vendor/github.com/prometheus/client_golang/NOTICE

...github.com/prometheus/client_golang/prometheus/.gitignore

.../github.com/prometheus/client_golang/prometheus/README.md

...ometheus/client_golang/prometheus/build_info_collector.go

...thub.com/prometheus/client_golang/prometheus/collector.go

...github.com/prometheus/client_golang/prometheus/counter.go

...or/github.com/prometheus/client_golang/prometheus/desc.go

vendor/github.com/prometheus/client_golang/prometheus/doc.go

...m/prometheus/client_golang/prometheus/expvar_collector.go

vendor/github.com/prometheus/client_golang/prometheus/fnv.go

...r/github.com/prometheus/client_golang/prometheus/gauge.go

...b.com/prometheus/client_golang/prometheus/go_collector.go

...prometheus/client_golang/prometheus/go_collector_go116.go

...rometheus/client_golang/prometheus/go_collector_latest.go

...thub.com/prometheus/client_golang/prometheus/histogram.go

...s/client_golang/prometheus/internal/go_runtime_metrics.go

...om/prometheus/client_golang/prometheus/internal/metric.go

.../github.com/prometheus/client_golang/prometheus/labels.go

.../github.com/prometheus/client_golang/prometheus/metric.go

...ithub.com/prometheus/client_golang/prometheus/observer.go