make headers thread safe

add reader lock

context.go

@@ -21,6 +21,7 @@ import (
 	"time"
 
 	"github.com/gin-contrib/sse"
+
 	"github.com/gin-gonic/gin/binding"
 	"github.com/gin-gonic/gin/render"
 )
@@ -983,6 +984,8 @@ func (c *Context) Status(code int) {
 // It writes a header in the response.
 // If value == "", this method removes the header `c.Writer.Header().Del(key)`
 func (c *Context) Header(key, value string) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
 	if value == "" {
 		c.Writer.Header().Del(key)
 		return
@@ -992,6 +995,8 @@ func (c *Context) Header(key, value string) {
 
 // GetHeader returns value from request headers.
 func (c *Context) GetHeader(key string) string {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
 	return c.requestHeader(key)
 }