handle HTTP 408 as retryable (#12)

Author: Dean Karn

.github/workflows/go.yml

@@ -42,4 +42,4 @@ jobs:
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v2
         with:
-          version: v1.43.0
+          version: v1.45.2

net/http/retryable.go

@@ -11,6 +11,7 @@ var (
 		http.StatusTooManyRequests:    true,
 		http.StatusBadGateway:         true,
 		http.StatusGatewayTimeout:     true,
+		http.StatusRequestTimeout:     true,
 
 		// 524 is a Cloudflare specific error which indicates it connected to the origin server but did not receive
 		// response within 100 seconds and so times out.