Initialize, Start Server and Create Database in Single Script

I am writing a provision script for a dev environment with the following:

sudo su - postgres <<EOF
cd ~/data
pg_ctl -D . initdb
pg_ctl -D . -l run.log start
createdb mydb
pg_ctl -D . stop
EOF

It fails with the following error:

createdb: could not connect to database template1: could not connect to server: No such file or directory
    Is the server running locally and accepting
    connections on Unix domain socket "/run/postgresql/.s.PGSQL.5432"?

Manually executing the commands works. I have noticed that when createdb succeeds, there are several postgres processes, often 5 or 6, so I added the following:

...
pg_ctl -D . -l run.log start
until [ `pgrep -c postgres` -gt 4 ]; do true; done
createdb mydb
...

But it hangs, meaning pgrep never gets over 5 counts inside the script runtime. I have also tried using a subshell:

...
(pg_ctl -D . -l run.log start)
wait
createdb mydb
...

With no success.