Fix `go get` instructions (#1271)

Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>

README.md

@@ -23,9 +23,9 @@ Going forward, all images shall be available at `quay.io/oauth2-proxy/oauth2-pro
 
 1.  Choose how to deploy:
 
-    a. Download [Prebuilt Binary](https://github.com/oauth2-proxy/oauth2-proxy/releases) (current release is `v7.1.0`)
+    a. Download [Prebuilt Binary](https://github.com/oauth2-proxy/oauth2-proxy/releases) (current release is `v7.1.3`)
 
-    b. Build with `$ go get github.com/oauth2-proxy/oauth2-proxy` which will put the binary in `$GOROOT/bin`
+    b. Build with `$ go get github.com/oauth2-proxy/oauth2-proxy/v7` which will put the binary in `$GOROOT/bin`
 
     c. Using the prebuilt docker image [quay.io/oauth2-proxy/oauth2-proxy](https://quay.io/oauth2-proxy/oauth2-proxy) (AMD64, ARMv6 and ARM64 tags available)