use golang 1.9

.travis.yml

@@ -1,7 +1,7 @@
 sudo: required
 language: go
 go:
-- 1.8.3
+- 1.9
 go_import_path: v2ray.com/core
 git:
   depth: 5

tools/release/release-ci.sh

@@ -25,7 +25,7 @@ gpg --import /v2ray/build/sign_key.asc
 curl -L -o /v2ray/build/releases https://api.github.com/repos/v2ray/v2ray-core/releases
 
 GO_INSTALL=golang.tar.gz
-curl -L -o ${GO_INSTALL} https://storage.googleapis.com/golang/go1.8.3.linux-amd64.tar.gz
+curl -L -o ${GO_INSTALL} https://storage.googleapis.com/golang/go1.9.linux-amd64.tar.gz
 tar -C /usr/local -xzf ${GO_INSTALL}
 export PATH=$PATH:/usr/local/go/bin