add Client::headers

awc/CHANGES.md

@@ -1,6 +1,9 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
+### Added
+* Add `Client::headers` to get default mut reference of `HeaderMap` of client object. 
+
 ### Changed
 * `ConnectorService` type is renamed to `BoxConnectorService` [#2081]
 

awc/src/lib.rs

@@ -286,4 +286,12 @@ impl Client {
         }
         req
     }
+
+    /// Get default HeaderMap of Client.
+    ///
+    /// Returns Some(&mut HeaderMap) when Client object is unique
+    /// (No other clone of client exists at the same time).
+    pub fn headers(&mut self) -> Option<&mut HeaderMap> {
+        Rc::get_mut(&mut self.0.headers)
+    }
 }