> ./server -h
Usage of ./server:
  -listen string
    	HTTP listen address (default ":8080")
  -proxy string
    	Optional comma-separated list of URLs to proxy uppercase requests

# in first terminal
./server --listen=localhost:8081

# in second terminal
./server --listen=localhost:8082

# in third terminal
./server --listen=localhost:8080 --proxy=localhost:8081,localhost:8082

> curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"s":"hello"}' \
  http://localhost:8080/count
{"v":5}
> curl --header "Content-Type: application/json" \
  --request POST \
  --data '{"s":"hello"}' \
  http://localhost:8080/uppercase
{"v":"HELLO"}