Added DefaultClient for compatiblity (it's an alias for fetch)

main.go

@@ -314,6 +314,9 @@ var Fetch = &Client{
 	Timeout:   20 * time.Second,
 }
 
+// DefaultClient is an alias for Fetch.
+var DefaultClient = Fetch
+
 func CanonicalHeaderKey(key string) string {
 	const allowedCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!#$%&'*+-.^_`|~"
 	for _, char := range []rune(key) {