build: switch to go install for installing dependencies

- Replace `go get -u -v` with `go install` for installing `gorush`

Signed-off-by: Bo-Yi Wu <[email protected]>

README.md

@@ -235,7 +235,7 @@ The pre-compiled binaries can be downloaded from [release page](https://github.c
 With `Go` installed
 
 ```sh
-go get -u -v github.com/appleboy/gorush
+go install github.com/appleboy/gorush
 ```
 
 On linux