PostgreSQL 9.6 - can't connect to database created from a custom template database - postgresql

Question

I have created a database foo which I am using as a template database to create other databases from.
I am running all PostgreSQL in a Docker container (not sure if that is relevant to the problem at hand).
Here is the (truncated) SQL
CREATE DATABASE foo WITH ENCODING 'UTF8' template0;
\i db_schema_foo.sql
-- Create extensions
-- Initialise db with data etc ...
CREATE DATABASE foobar TEMPLATE foo;
(Truncated) console output:
CREATE DATABASE
You are now connected to database "foo" as user "postgres".
CREATE TABLE
CREATE INDEX
CREATE TABLE
CREATE INDEX
CREATE TABLE
...
CREATE INDEX
CREATE TABLE
CREATE INDEX
CREATE TABLE
CREATE TABLE
CREATE TABLE
CREATE TABLE
CREATE TABLE
CREATE TABLE
CREATE INDEX
CREATE TABLE
CREATE INDEX
CREATE TABLE
CREATE INDEX
CREATE INDEX
CREATE INDEX
CREATE DATABASE
FATAL: database "foobar" does not exist
psql:/docker-entrypoint-initdb.d/create_databases.sql:82: \connect: FATAL: database "foobar" does not exist
From the console, I'm assuming that both foo and foobar are created - so why can't I connect to database foobar?

Answer 1

Use the psql command \l to see which databases exist.
I would expect database foobar to not exist.
That would mean that the CREATE DATABASE statement has failed.
Can you get the error message for that?
My suspicion is that creating the database failed because you were still connected to the template database foo. You can only use a database with no active connections as template.

Answer 2

CREATE DATABASE in output means either that databse was successfully created, if there would be error and no warning, like here:
t=# set client_min_messages TO fatal;
SET
t=# create database t;
t=# set client_min_messages TO warning;
SET
t=# create database t;
ERROR: database "t" already exists
there would not be such output - CREATE DATABASE
so next line FATAL: database "foobar" does not exist (together with knowledge database was created) leads to idea that OP is connecting to different cluser, or different database
In private chat we found that database created was "Foobar" and database attempting to connect was Foobar and thus "foobar", which does not exist indeed, as "Foobar" does