TUN-4067: Reformat code for consistent import order, grouping, and fix formatting. Added goimports target to the Makefile to make this easier in the future.

connection/metrics.go

@@ -4,8 +4,9 @@ import (
 	"sync"
 	"time"
 
-	"github.com/cloudflare/cloudflared/h2mux"
 	"github.com/prometheus/client_golang/prometheus"
+
+	"github.com/cloudflare/cloudflared/h2mux"
 )
 
 const (
@@ -414,4 +415,4 @@ func newTunnelMetrics() *tunnelMetrics {
 		tunnelMetricsInternal.metrics = initTunnelMetrics()
 	})
 	return tunnelMetricsInternal.metrics
-}
+}