gcloud compute: configure firewall for external traffic

I am attempting to configure my google cloud instance to allow external traffic so I can set up a web socket; however despite adding a rule for all external TCP/IP traffic, I can't access it. My rules are:

gcloud compute firewall-rules list
NAME              NETWORK SRC_RANGES RULES   SRC_TAGS TARGET_TAGS
default-allow-ssh default 0.0.0.0/0  tcp:22
external-traffic  default 0.0.0.0/0  tcp,udp


gcloud compute instances list
NAME      ZONE          MACHINE_TYPE  PREEMPTIBLE INTERNAL_IP EXTERNAL_IP    STATUS
pi-server us-central1-a n1-standard-1             **.***.*.*  **.***.***.*** RUNNING

I have configured this as a static IP (this is displayed in my cloud dashboard):

Name	           External Address	Region	    Type	In use by
crypto-iris-******	**.***.***.***	us-central1	Static	VM instance my_instance_name (Zone a)	

I also have some Go client/server web socket code that works perfectly on my computer using localhost:8080 as address. So, my question is: can I simply replace localhost with the external static IP of my instance under these rules?

My client makes use of "github.com/gorilla/websocket" on port 8080. Output of client locally is:

connecting to ws://23.251.148.133:8080/echo
dial:dial tcp 23.251.148.133:8080: getsockopt: operation timed out
exit status 1

Code upon request, if anyone wants to see it.

Problem: my golang/gorilla server was hosting on localhost:8080. I changed it to 0.0.0.0:8080. Smooth sailing after that.

See following post about this, but basically the server was listening to the local loopback address (available only to local machine) instead of the outside world.

https://serverfault.com/questions/78048/whats-the-difference-between-ip-address-0-0-0-0-and-127-0-0-1