fix calculator example code script
set -x
set -e
-cargo build
-./target/debug/calculator server 127.0.0.1:6569 &
+cargo build --package calculator
+../../../target/debug/calculator server 127.0.0.1:6569 &
SERVER=$!
sleep 1
-./target/debug/calculator client 127.0.0.1:6569
+../../../target/debug/calculator client 127.0.0.1:6569
kill $SERVER
