New function GetReason to get HTTP reason phrase from an http.Request

http/reason.go

@@ -0,0 +1,14 @@
+package http
+
+import (
+	"net/http"
+	"strings"
+)
+
+func GetReason(r *http.Response) string {
+	if i := strings.IndexByte(r.Status, ' '); i != -1 {
+		return r.Status[i+1:]
+	} else {
+		return ""
+	}
+}