You do not need to go down the Github rabbit hole. The symbol prometheus is from the package github.com/prometheus/client_golang/prometheus. Use go doc github.com/prometheus/client_golang/prometheus to read the documentation from your local copy of the package. Use go list -f {{.Dir}} github.com/prometheus/client_golang/prometheus to find out where your local copy is located. If there is only one prometheus.NewGaugeVec in your workspace, then the command go doc prometheus.NewGaugeVec shows the documentation for function and reports the package where it's defined.