I had the same error on PHP 7.3.7 docker with laravel:
This works for me
apt-get update && apt-get install -y libpq-dev && docker-php-ext-install pdo pgsql pdo_pgsql
This will install the pgsql and pdo_pgsql drivers.
Now run this command to uncomment the lines extension=pdo_pgsql.so and extension=pgsql.so from php.ini
sed -ri -e 's!;extension=pdo_pgsql!extension=pdo_pgsql!' $PHP_INI_DIR/php.ini
sed -ri -e 's!;extension=pgsql!extension=pgsql!' $PHP_INI_DIR/php.ini