diff --git a/pkg/httpclient/request.go b/pkg/httpclient/request.go
index e16f0e0..095bee9 100644
--- a/pkg/httpclient/request.go
+++ b/pkg/httpclient/request.go
@@ -36,6 +36,9 @@ type Request struct {
 func (c *Request) Header(key, value string) *Request {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+	if c.header == nil {
+		c.header = map[string][]string{}
+	}
 	c.header.Add(key, value)
 	if strings.ToLower(key) == "content-type" {
 		c.contentType = value
@@ -66,11 +69,19 @@ func (c *Request) GET(url string) *Request {
 func (c *Request) ContentType(value string) *Request {
 	c.mutex.Lock()
 	defer c.mutex.Unlock()
+	if c.header == nil {
+		c.header = map[string][]string{}
+	}
 	c.header.Set("Content-Type", value)
 	c.contentType = value
 	return c
 }
 
+func (c *Request) WithContentTypeAsJson() *Request {
+	c.ContentType("application/json")
+	return c
+}
+
 // WithHost 添加请求头host
 func (c *Request) WithHost(host string) *Request {
 	c.host = host