Inject context to Client

[liubin]

For passing context to server side, we need accept context as an additional parameter.

This will need some modify in these parts( take sync as an example):

• codegen

Add new parameter to generated code:

diff --git a/compiler/src/codegen.rs b/compiler/src/codegen.rs
index da3d24e..64945f1 100644
--- a/compiler/src/codegen.rs
+++ b/compiler/src/codegen.rs
@@ -212,7 +212,7 @@ impl<'a> MethodGen<'a> {
     // Method signatures
     fn unary(&self, method_name: &str) -> String {
         format!(
-            "{}(&self, req: &{}, timeout_nano: i64) -> {}<{}>",
+            "{}(&self, req: &{}, timeout_nano: i64, metadata: ::ttrpc::TtrpcContext) -> {}<{}>",
             method_name,
             self.input(),
             fq_grpc("Result"),
@@ -314,7 +314,7 @@ impl<'a> MethodGen<'a> {
                         self.output()
                     ));
                     w.write_line(&format!(
-                        "::ttrpc::client_request!(self, req, timeout_nano, \"{}.{}\", \"{}\", cres);",
+                        "::ttrpc::client_request!(self, req, timeout_nano, metadata, \"{}.{}\", \"{}\", cres);",
                         self.package_name,
                         self.service_name,
                         &self.proto.get_name(),

• client_handler macro

Accept the parameter and set to Request:

--- a/src/sync/utils.rs
+++ b/src/sync/utils.rs
@@ -70,11 +70,12 @@ macro_rules! request_handler {
 /// Send request through sync client.
 #[macro_export]
 macro_rules! client_request {
-    ($self: ident, $req: ident, $timeout_nano: ident, $server: expr, $method: expr, $cres: ident) => {
+    ($self: ident, $req: ident, $timeout_nano: ident, $metadata: ident, $server: expr, $method: expr, $cres: ident) => {
         let mut creq = ::ttrpc::Request::new();
         creq.set_service($server.to_string());
         creq.set_method($method.to_string());
         creq.set_timeout_nano($timeout_nano);
+        creq.set_metadata($metadata);