Replace usage of http.DefaultClient and http.DefaultTransport (#104135)

Remove usage of http.DefaultClient and http.DefaultTransport

Part of grafana/data-sources#484

pkg/build/cmd/grafanacom.go

@@ -2,10 +2,12 @@ package main
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"fmt"
 	"io"
 	"log"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
@@ -26,6 +28,23 @@ import (
 
 const grafanaAPI = "https://grafana.com/api"
 
+var httpClient = http.Client{
+	Transport: &http.Transport{
+		Proxy: http.ProxyFromEnvironment,
+		DialContext: func(dialer *net.Dialer) func(context.Context, string, string) (net.Conn, error) {
+			return dialer.DialContext
+		}(&net.Dialer{
+			Timeout:   30 * time.Second,
+			KeepAlive: 30 * time.Second,
+		}),
+		ForceAttemptHTTP2:     true,
+		MaxIdleConns:          100,
+		IdleConnTimeout:       90 * time.Second,
+		TLSHandshakeTimeout:   10 * time.Second,
+		ExpectContinueTimeout: 1 * time.Second,
+	},
+}
+
 // GrafanaCom implements the sub-command "grafana-com".
 func GrafanaCom(c *cli.Context) error {
 	bucketStr := c.String("src-bucket")
@@ -330,7 +349,7 @@ func postRequest(cfg packaging.PublishConfig, pth string, body any, descr string
 		return nil
 	}
 
-	resp, err := http.DefaultClient.Do(req)
+	resp, err := httpClient.Do(req)
 	if err != nil {
 		return fmt.Errorf("failed posting to %s (%s): %s", u, descr, err)
 	}