fix: typo (#3006)

context.go

@@ -843,7 +843,7 @@ func (c *Context) GetHeader(key string) string {
 	return c.requestHeader(key)
 }
 
-// GetRawData return stream data.
+// GetRawData returns stream data.
 func (c *Context) GetRawData() ([]byte, error) {
 	return ioutil.ReadAll(c.Request.Body)
 }