add HeaderToString for req and resp

req.go

@@ -1,6 +1,7 @@
 package req
 
 import (
+	"bytes"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -145,3 +146,13 @@ func cloneMap(h map[string]string) map[string]string {
 	}
 	return m
 }
+
+// convertHeaderToString converts http header to a string.
+func convertHeaderToString(h http.Header) string {
+	if h == nil {
+		return ""
+	}
+	buf := new(bytes.Buffer)
+	h.Write(buf)
+	return buf.String()
+}

request.go

@@ -143,6 +143,11 @@ func (r *Request) TraceInfo() TraceInfo {
 	return ti
 }
 
+// HeaderToString get all header as string.
+func (r *Request) HeaderToString() string {
+	return convertHeaderToString(r.Headers)
+}
+
 // SetURL set the url for request.
 func (r *Request) SetURL(url string) *Request {
 	r.RawURL = url

response.go

@@ -212,3 +212,11 @@ func (r *Response) GetHeaderValues(key string) []string {
 	}
 	return r.Header.Values(key)
 }
+
+// HeaderToString get all header as string.
+func (r *Response) HeaderToString() string {
+	if r.Response == nil {
+		return ""
+	}
+	return convertHeaderToString(r.Header)
+}