Imports cloud.google.com/go/compute/metadata contrib.go.opencensus.io/exporter/stackdriver contrib.go.opencensus.io/exporter/stackdriver/propagation go.opencensus.io/plugin/ochttp go.opencensus.io/trace golang.org/x/oauth2/google Standard library imports context crypto/tls fmt log net/http net/http/httptrace os strings