Drop all schemas from a database postgresql

dropSchemas.sql

SET search_path = _global, pg_catalog;

CREATE OR REPLACE FUNCTION drop_all () 
   RETURNS VOID  AS
   $$
   DECLARE rec RECORD; 
   BEGIN
       -- Get all the schemas
        FOR rec IN
        select distinct schemaname
         from pg_catalog.pg_tables
         -- You can exclude the schema which you don't want to drop by adding another condition here
         where schemaname not like 'pg_catalog'  
           LOOP
             EXECUTE 'DROP SCHEMA ' || rec.schemaname || ' CASCADE'; 
           END LOOP; 
           RETURN; 
   END;
   $$ LANGUAGE plpgsql;

select drop_all();

Another version based on pg_catalog.pg_namespace:

CREATE OR REPLACE FUNCTION drop_all () 
   RETURNS VOID  AS
   $$
   DECLARE rec RECORD; 
   BEGIN
       -- Get all the schemas
        FOR rec IN
        SELECT nspname FROM pg_catalog.pg_namespace WHERE (nspname NOT LIKE 'pg_%') and (nspname != 'information_schema')
           LOOP
             EXECUTE 'DROP SCHEMA ' || rec || ' CASCADE'; 
           END LOOP; 
           RETURN; 
   END;
   $$ LANGUAGE plpgsql;

SELECT drop_all();

changing the EXECUTE statement works for me
EXECUTE format('DROP SCHEMA "%s" CASCADE', rec.nspname);