client: add proxy option (#1885)

* client: add proxy option

* client: add WithProxy CallOption

* use address option

* ProxyAddress => Proxy

client/options.go

@@ -17,6 +17,8 @@ import (
 type Options struct {
 	// Used to select codec
 	ContentType string
+	// Proxy address to send requests via
+	Proxy string
 
 	// Plugged interfaces
 	Broker    broker.Broker
@@ -149,6 +151,13 @@ func ContentType(ct string) Option {
 	}
 }
 
+// Proxy sets the proxy address
+func Proxy(addr string) Option {
+	return func(o *Options) {
+		o.Proxy = addr
+	}
+}
+
 // PoolSize sets the connection pool size
 func PoolSize(d int) Option {
 	return func(o *Options) {